Deuteronomy 21:15-17 requires a man with two wives to recognize the birthright of his firstborn son, even if his mother is the less favored wife. This law is intertextually linked to Jacob’s giving Reuben’s firstborn rights to Joseph in Genesis, but it can also be read as a response to Abraham’s disinheriting Ishmael in favor of his younger son, Isaac.

The Status of Firstborn Sons

In biblical and ancient Near Eastern law,[1] the firstborn son (בכור, bәkôr) held a privileged position and received the birthright (בכורה, bәkōrāh). Although this is not clear in the Bible, we know from other ancient Near Eastern societies, that the firstborn son had certain obligations as well, including the following responsibilities upon the death of his father:[2]

Carry on the father’s name (patronym);

Manage the family estate;

Provide for minors in the family;

Provide a dowry for unmarried sisters;

Pay for his parents’ burial and mourning ceremonies and maintain their grave afterwards.

The firstborn would receive a double portion (שנים פי, pî šәnaîm) of inheritance,[3] a right reflected in both the biblical and ANE legal texts,[4] perhaps to help pay for these duties.

Two Wives, Two Sons: The Law

Although not a very common practice, ancient Near Eastern societies, including ancient Israel, were polygynous: men could have more than one wife.[5] What, then, if a man has a preferred or main wife and he wishes to give the birthright (בכורה) to the oldest son of that wife and not to his actual “firstborn son” (בכור)? The law of Deuteronomy 21:15–17 addresses this “worst case scenario”:

דברים כא:טו כִּי תִהְיֶיןָ לְאִישׁ שְׁתֵּי נָשִׁים הָאַחַת אֲהוּבָה וְהָאַחַת שְׂנוּאָה וְיָלְדוּ לוֹ בָנִים הָאֲהוּבָה וְהַשְּׂנוּאָה וְהָיָה הַבֵּן הַבְּכוֹר לַשְּׂנִיאָה. כא:טז וְהָיָה בְּיוֹם הַנְחִילוֹ אֶת בָּנָיו אֵת אֲשֶׁר יִהְיֶה לוֹ לֹא יוּכַל לְבַכֵּר אֶת בֶּן הָאֲהוּבָה עַל פְּנֵי בֶן הַשְּׂנוּאָה הַבְּכֹר. כא:יז כִּי אֶת הַבְּכֹר בֶּן הַשְּׂנוּאָה יַכִּיר לָתֶת לוֹ פִּי שְׁנַיִם בְּכֹל אֲשֶׁר יִמָּצֵא לוֹ כִּי הוּא רֵאשִׁית אֹנוֹ לוֹ מִשְׁפַּט הַבְּכֹרָה.

Deut 21:15 If a man has two wives, one of them loved and the other unloved, and if both the loved and the unloved have borne him sons, the firstborn being the son of the one who is unloved, 21:16 then on the day when he wills his possessions to his sons, he is not permitted to treat the son of the loved as the firstborn in preference to the son of the unloved, who is the firstborn. 21:17 He must acknowledge as firstborn the son of the one who is unloved, giving him a double portion of all that he has; since he is the first issue of his virility, the right of the firstborn is his.

This law was designed to protect the rights of the firstborn son even if his mother is not the favored wife.

Leah and Rachel: Reuben and Joseph

This case of a favored wife and her firstborn plays an important role in the Jacob and Joseph narratives. According to Genesis, Jacob marries two sisters, Leah and Rachel. The latter he loves and the former he does not. Nevertheless, Rachel has trouble getting pregnant, while God makes Leah fertile immediately:

בראשית כט:לא וַיַּרְא יְ-הוָה כִּי שְׂנוּאָה לֵאָה וַיִּפְתַּח אֶת רַחְמָהּ וְרָחֵל עֲקָרָה.

Gen 29:31 When YHWH saw that Leah was spurned,[6] he opened her womb; but Rachel was barren.

Leah’s son Reuben was Jacob’s firstborn, and should have received the inheritance and rights of the firstborn, as opposed to Rachel’s firstborn son, Joseph. And yet, Genesis strongly implies, even if it does not say this outright, that Joseph and not Reuben is given the birthright.

Reuben Rejected

When Jacob blesses his sons at the end of Genesis, Reuben is not blessed but cursed:

בראשית מט:ג רְאוּבֵן בְּכֹרִי אַתָּה כֹּחִי וְרֵאשִׁית אוֹנִי יֶתֶר שְׂאֵת וְיֶתֶר עָז. מט:דפַּחַז כַּמַּיִם אַל תּוֹתַר כִּי עָלִיתָ מִשְׁכְּבֵי אָבִיךָ אָז חִלַּלְתָּ יְצוּעִי עָלָה.

Gen 49:3 Reuben, you are my firstborn, my might and first fruit of my vigor, exceeding in rank and exceeding in honor. 49:4 Unstable as water, you shall excel no longer; for when you mounted your father’s bed, you brought disgrace — my couch he mounted!

The poem here explicitly recognizes Reuben’s status as firstborn but appears to explain why he is being rejected by his father. In fact, the account of Reuben’s sin with Bilhah (Gen 35:22) may be designed to provide Jacob with a reason for overlooking Reuben’s rights in favor of Joseph. The 16th century Italian Jewish commentator, R. Ovadiah Seforno, understands the episode and Jacob’s reaction this way (Deut 21:16):

לֹא יַעֲבִיר הַבְּכוֹרָה מִן הַבֵּן בִּשְׁבִיל שִׂנְאַת זוֹ אוֹ אַהֲבַת זוֹ. אֲבָל אִם יַעֲשֶׂה זֶה בְּסִבַּת רִשְׁעַת הַבֵּן הַבְּכוֹר, אָז רָאוּי לְהַעֲבִיר, כְּאָמְרָם זַ”ל: אִם לא הָיָה נוֹהֵג כַּשּׁוּרָה, זָכוּר לְטוֹב. וְכֵן נִרְאֶה שֶׁעָשָׂה יַעֲקב אָבִינוּ…

A man may not remove the birthright from his son because he dislikes one and loves another. But, if he does so because the firstborn is wicked, then it is a worthy act to do so, as the Sages said [regarding a father who disinherits his sons in favor of others] “If [the son] does not live in a befitting manner, then [the father who disinherits him] will be remembered for the good” (m. Baba Batra 8:5) And it would appear that this is what Jacob did…[7]

Joseph Receives the Birthright

In contrast, in the previous chapter in Genesis, in his private conversation with Joseph, Jacob tells him that he is receiving an extra portion, beyond that of his brothers:

בראשית מח:כב וַאֲנִי נָתַתִּי לְךָ שְׁכֶם אַחַד עַל אַחֶיךָ אֲשֶׁר לָקַחְתִּי מִיַּד הָאֱמֹרִי בְּחַרְבִּי וּבְקַשְׁתִּי.

Gen 48:22 And now, I assign to you one portion (šәkem)[8] more than to your brothers, which I wrested from the Amorites with my sword and bow.”

This verse suggests that Joseph is being given the double portion due the firstborn. This is implied earlier in the chapter as well:

בראשית מח:ה וְעַתָּה שְׁנֵי בָנֶיךָ הַנּוֹלָדִים לְךָ בְּאֶרֶץ מִצְרַיִם עַד בֹּאִי אֵלֶיךָ מִצְרַיְמָה לִי הֵם אֶפְרַיִם וּמְנַשֶּׁה כִּרְאוּבֵן וְשִׁמְעוֹן יִהְיוּ לִי.

Gen 48:5 Now, your two sons, who were born to you in the land of Egypt before I came to you in Egypt, shall be mine; Ephraim and Manasseh shall be mine no less than Reuben and Simeon.

It is possible that Jacob’s blessing here about Ephraim and Manasseh and the blessing about the extra portion are doublets, i.e., stories from two different sources, each grounding the double portion of the Joseph tribes in its own way.[9] Alternatively, Rashbam (R. Samuel ben Meir, 1085-1158) suggests a wholistic reading according to which the extra-portion-blessing refers to Jacob’s adoption of Ephraim and Manasseh (Gen 48:22).[10]

Joseph Replaces Reuben

In either case, a comparison of these texts about Joseph’s double portion and Jacob’s curse of Reuben implies that Joseph is receiving the birthright in place of Reuben, as Rashbam already noted (Gen 48:5).

ועתה שני בניך וגו’ – כלומר: מאחר שנתן לי הקב”ה את ארץ כנען, הרי ברשותי לעשותך בכור ליטול פי שני שבטים, ולכך שני בניך יטלו כנגד ראובן ושמעון.

“Now your two sons” – meaning, since the Holy One, blessed by He, gave me the land of Canaan, it is in my power to make you the firstborn to receive two tribes, and therefore, your two sons will receive [inheritance] in the same manner as Reuben and Simeon.

The late book of Chronicles, which knows the Torah, makes explicit what is implicit in Genesis:

דברי הימים א ה:א וּבְנֵי רְאוּבֵן בְּכוֹר יִשְׂרָאֵל כִּי הוּא הַבְּכוֹר וּבְחַלְּלוֹ יְצוּעֵי אָבִיו נִתְּנָה בְּכֹרָתוֹ לִבְנֵי יוֹסֵף בֶּן יִשְׂרָאֵל וְלֹא לְהִתְיַחֵשׂ לַבְּכֹרָה.

1 Chron 5:1 The sons of Reuben the first-born of Israel, for he was the first-born. But when he defiled his father’s bed, his birthright was given to the sons of Joseph son of Israel, so he is not reckoned as first-born in the genealogy.

Most likely, Genesis is never explicit about this transference of birthright because its editors were uncomfortable with Jacob’s blatant violation of Israelite norms. What Jacob does with Reuben and Joseph, the firstborn sons respectively of his unloved wife and loved wife, violates the inheritance laws reflected in Deuteronomy. Reuben’s sin gives Jacob a special reason to do so, but Deuteronomy doesn’t list any exceptions to the rule.

Carmichael’s Law and Narrative Approach

It is clear that the Reuben/Joseph birthright issue has a connection with the law in Deuteronomy, both in the explicit description of Leah and Rachel as unloved and loved, and in the description of a firstborn as “first issue of [a father’s] vigor” (ראשית און), a rare biblical expression:[11]

Curse of Reuben (Gen 49:3) Law of the Firstborn (Deut 21:17) Reuben, you are my firstborn, my might and first issue of my vigor, exceeding in rank and exceeding in honor. He must acknowledge as firstborn the son of the one who is unloved, giving him a double portion of all that he has; since he is the first issue of his vigor, the right of the firstborn is his. רְאוּבֵן בְּכֹרִי אַתָּה כֹּחִי וְרֵאשִׁית אוֹנִי יֶתֶר שְׂאֵת וְיֶתֶר עָז. כִּי אֶת הַבְּכֹר בֶּן הַשְּׂנוּאָה יַכִּיר לָתֶת לוֹ פִּי שְׁנַיִם בְּכֹל אֲשֶׁר יִמָּצֵא לוֹ כִּי הוּא רֵאשִׁית אֹנוֹ לוֹ מִשְׁפַּט הַבְּכֹרָה.

But which is the earlier text?

In a series of books and articles, Calum Carmichael, Professor Emeritus of comparative literature and law at Cornell University, has argued that biblical law collections were written in reaction to biblical narratives.[12] In this case, he claimed that Deuteronomy 21’s “law of the two wives” was a response to the Reuben and Joseph story.[13] Carmichael hypothesizes that,

[Biblical laws] seek out and evaluate the first occurrence of a problem in the nation’s history, one invariably idiosyncratic in nature and address a similar, less idiosyncratic problem that might arise in the future.[14]

In other words, narratives are complex, as they involve plot elements, character development, and other literary features. Laws, thus, cannot be written to address narratives directly but, he argues, the laws are an attempt to abstract the key problems in biblical narratives and offer solutions.

In this case, the law ignores the idiosyncratic aspects of Reuben’s sin or Joseph’s dreams and instead deals with the core problem of favoring the son of a beloved wife over the son of a less beloved wife, and thus, unfairly taking away his rightful inheritance, as happened with Reuben.

Strong Intertextual Links

Though I do find Carmichael’s readings persuasive, or at least intriguing, his view of how biblical law developed is strongly disputed by many scholars, some of whom have offered systemic critiques of many aspects of his method of interpretation.[15] But whether the law in Deuteronomy is responding to the Genesis account, or whether the Genesis account is dealing with the law in Deuteronomy, the intertextual connection between the two is strong. In fact, Midrash Tanhuma (late first millennium C.E.) reads Deuteronomy 21:16 as referring directly to what Jacob did with Reuben and Joseph (Vayetzei 13):

כי (תהיינה) [תהיין] לאיש שתי נשים – זה יעקב… שתי נשים לאה ורחל, אחת אהובה – זו רחל, שנאמר ויאהב גם את רחל. והאחת שנואה – זו לאה, שנאמר וירא ה’ כי שנואה לאה… לא יוכל לבכר את בן האהובה – ליוסף, למה כי את הבכור בן השנואה יכיר – זה ראובן, שנאמר ראובן בכורי אתה…

“If a man has two wives” – this refers to Jacob… “Two wives” – Leah and Rachel. “One loved” – this is Rachel, for it says (Gen 29:30): “And he loved Rachel.” “And one unloved” – this is Leah, for it says (Gen 29:31): “And the Lord saw that Leah was unloved.”… “He may not give the son of the loved wife the birthright” – to Joseph. And why not? “For he must recognize the birthright of the firstborn son of the unloved wife” – this is Reuben, as it says (Gen 49:3): “Reuben you are my firstborn son.”…

Though Midrash Tanhuma takes an apologetic approach, arguing that Jacob didn’t give the birthright to Joseph but actually recognized Reuben’s claim, this midrash underscores the clear connection between the texts. Ironically, I believe that this very clear and strong connection has masked links to another tale dealing with the same problem, and that the law in Deuteronomy is responding to both of these cases.

Hagar and Sarah: Ishmael and Isaac

Genesis 16 and 21 tell of Abraham’s two wives, Sarah and Hagar, whose sons compete for firstborn status. This is not a standard case of polygyny, like Jacob’s marriages to Leah and Rachel, wherein the two women are of equal status, but what anthropologists call polycoity, a marriage with wives of unequal social status.

Sarah is Abraham’s primary wife, and Hagar is her maidservant [16] (שפחה or אמה). Nevertheless, when Sarah takes (לקח) her maidservant and gives (נתן) her to Abram as a wife (אשה), the text uses the standard biblical phraseology for marriage, and thus leaves no doubt that a marriage took place between Abram and Hagar (Gen 16:3).[17] Hagar now has a dual status in the household: she is Sarah’s maidservant and Abraham’s secondary wife, but not his maidservant.[18] This is an important point when it comes to determining whether Ishmael could have been Abraham’s heir.

Does Ishmael have a Legitimate Claim to the Birthright? (Gen 21)

Ishmael is clearly Abram’s firstborn (בכור). But the law in Deuteronomy 21 never discusses what happens if one of the man’s wives is also a maidservant to a primary wife. Does the child count as one of his sons? Kinship studies note that the firstborn child of the primary wife will automatically receive the birthright,[19] though Deuteronomy could be read as a blanket rule rejecting this distinction.

But even if the law in Deuteronomy would not apply to cases of polycoity, sons of secondary wives should at least inherit something along with their brothers. This is supported by the Laws of Hammurabi (LH) §170, and by the Laws of Lipit-Ishtar (LI) §24, which state that the children of the first and second wife will share equally the property of their father. Certainly, this is what happens with Jacob’s four sons with Bilhah and Zilpah, who were maidservants, since all of Jacob’s sons inherited equally (with Joseph receiving the birthright of course).

But Sarah demands that that Abraham cast off Ishmael entirely:

בראשית כא:י וַתֹּאמֶר לְאַבְרָהָם גָּרֵשׁ הָאָמָה הַזֹּאת וְאֶת בְּנָהּ כִּי לֹא יִירַשׁ בֶּן הָאָמָה הַזֹּאת עִם בְּנִי עִם יִצְחָק.

Gen 21:10 She said to Abraham, “Cast out[20]that slave-woman and her son, for the son of that slave shall not share in the inheritance with my son Isaac.”

In other words, Sarah demands that Isaac be considered Abraham’s only heir and that Ishmael not inherit at all.[21] This certainly violates the ethos of Deuteronomy’s law of the firstborn, namely, that sons not be mistreated based on which mother they have.

Sarah is essentially demanding that Abraham treat Ishmael as if he were not his son, which flies in the face of how Abraham treats Ishmael up to this point, who certainly acknowledges Ishmael as his son, since he names him (16:15) and has him circumcised (17:25-26). In fact, when describing Abraham’s reaction to Sarah’s demand to turn him out, the narrator says:

בראשית כא:ח וַיֵּרַע הַדָּבָר מְאֹד בְּעֵינֵי אַבְרָהָם עַל אוֹדֹת בְּנוֹ.

Gen 21:11 The matter concerning his son distressed Abraham greatly.

In short, by all accounts, Ishmael held a legitimate claim to a share in Abraham’s property and was perhaps even due the birthright.

As noted, Abraham is distressed about Sarah’s demand to send Ishmael away. His discomfort would be in keeping with the law in Deuteronomy 21, which is why the Torah here needs to explain why Ishmael is not permitted to take his rightful place as Abraham’s heir, just as it needed to explain why Reuben loses the birthright.

This seems to be the point of the verse introducing Sarah’s reaction:

בראשית כא:ט וַתֵּרֶא שָׂרָה אֶת בֶּן הָגָר הַמִּצְרִית אֲשֶׁר יָלְדָה לְאַבְרָהָם מְצַחֵק.

Gen 21:9 Sarah saw the son whom Hagar the Egyptian had borne to Abraham playing (məṣaḥēq).

The exact meaning of “playing” is not clear. It could just means the boy was playing and Sarah just didn’t want competition for Isaac around. Some literary scholars such as Robert Alter have noted that having Ishmael “play” or “laugh,” a word whose root is literally the root of Isaac’s name, implies that he was taking the place of Isaac, perhaps in Abraham’s mind, and this is what made Sarah jealous.[22]

Ishmael’s Sin

Although these reading are possible, it seems more likely to me that the term is meant to have a negative connotation.[23] For example, the term could be translated as “taunting” so perhaps he was making fun of Isaac or even of Abraham (Radak and Seforno ad loc.).[24] More sinister still, the root often has sexual connotations (Rashi ad loc., based on R. Akiva); Isaac himself will be seen “playing” with his wife Rebekah later on (Gen 26:8) and the Israelites get up “to play” after building the golden calf (Exod 32:6), which is often understood in the sexual sense.

Joseph Fleischman points to the semantic range of צ.ח.ק and its Akkadian cognate ṣâḫu as sharing an etymological meaning: to play, joke, amuse oneself sexually.[25] In fact, the Akkadian cognate has an explicitly dark sexual meaning: to entice someone to sexual actions against the accepted norm (CAD Ṣ 64–65).

It thus seems likely that the text wants to communicate that Ishmael was behaving in a sexually inappropriate manner, perhaps with the two-year-old Isaac himself, if we follow the LXX’s fuller text which adds “with her son Isaac” (μετὰ Ισαακ τοῦ υἱοῦ αὐτῆς) to the end of the verse. If so, then Genesis 21:9, like Genesis 35:22, was designed to give the patriarch a reason to disinherit his eldest son.[26]

God’s Involvement

But the text does not stop with this. Rather, the Torah further smooths over any discomfort by having God step in and dictate the course of events, declaring that Abraham must listen to Sarah because Isaac is Abraham’s true and only heir:

בראשית כא:יב וַיֹּאמֶר אֱלֹהִים אֶל אַבְרָהָם אַל יֵרַע בְּעֵינֶיךָ עַל הַנַּעַר וְעַל אֲמָתֶךָ כֹּל אֲשֶׁר תֹּאמַר אֵלֶיךָ שָׂרָה שְׁמַע בְּקֹלָהּ כִּי בְיִצְחָק יִקָּרֵא לְךָ זָרַע.כא:יג וְגַם אֶת בֶּן הָאָמָה לְגוֹי אֲשִׂימֶנּוּ כִּי זַרְעֲךָ הוּא.

Gen 21:12 But God said to Abraham, “Do not be distressed because of the boy and because of your slave woman; whatever Sarah says to you, do as she tells you, for it is through Isaac that offspring shall be named for you. 21:13 As for the son of the slave woman, I will make a nation of him also, because he is your offspring.”

The unstated point here is that Abraham’s progeny are being hand-picked by God for a special purpose; otherwise, Abraham would have been correct that Ishmael should inherit with Isaac and perhaps even, following the letter of the law as presented in Deuteronomy, have been his heir.[27] The phrase “for it is through Isaac that offspring shall be named for you” tips us off that Isaac should receive the status of “firstborn.” As mentioned above, one of the main duties of the firstborn was to carry one the father’s name.

Ishmael’s Case against Abraham

Genesis Rabbah (mid-first millennium C.E.) highlights the problem in a midrashic legend set in the time of Alexander the Great (Chayei Sarah 61; Theodor-Albeck):

בימי אלכסנדרוס מקדון באו בני ישמעאל ליעור על ישראל על הבכורה… אמר גביעה בן קוסם אני הולך ודן עימהם… אמר להן אלכסנדרוס מקדון מי תובע מיד מי, אמרו ישמעאלים אנו תובעין ומתורתם אנו באים עליהן כי את הבכור בן השנואה יכיר וגו’ (דברים כא יז) וישמעאל בכור הוא, אמר לו גביעה בן קוסם אדוני המלך אין אדם עושה בבניו מה שירצה, אמר לו הן, והא כת’ ויתן אברהם את כל אשר לו ליצחק, אמ’ ואיכן הוא לוקטור, אמר לו ולבני הפילגשים וגו’ [נתן אברהם מתנות] ונסתלקו בבושת פנים.

In the days of Alexander of Macedon, the Ishmaelites came with a claim against the Jews about the birthright… Geviah ben Qosem said: “I will go [on behalf of the Jews] to court with them.” … Alexander of Macedon said: “Who is suing whom?” The Ishmaelites said: “We are suing, and we are basing our claim on their own Torah, [which says] ‘he must recognize the birthright of the firstborn son of the unloved wife, etc.’ (Deut 21:17) And Ishmael was the firstborn!” Geviah ben Qosem said to him (Alexander): “My master the king, cannot a father do what he likes with his sons?” He (Alexander) responded: “Yes.” [Geviah continued]: “And does [the Torah] not say: “Abraham gave everything he had to Isaac.” [Alexander asked]: “But where does he act as legator (i.e., give gifts to other children)?”[28] [Geviah] said to him (Gen 25:6): “And to the sons of the concubines… [Abraham gave gifts].” [The Ishmaelites] left humiliated.

In this story, Geviah succeeds in answering the question on a technical halakhic level, pointing out that by giving the sons of the concubines gifts, Abraham fulfilled the letter of the law and was free to give the bulk of the inheritance to his chosen son, Isaac. Nevertheless, irrespective of Geviah’s shrewd response, the moral problem which undergirds the Deuteronomic law stands.

Deuteronomy 21:15-17 in Light of the Sarah-Hagar Story

The parallels between Deuteronomy 21 and the Ishmael stories are not perfect. For one, the text never states that Abram dislikes Hagar. Moreover, the text gives every indication that Abraham loves Ishmael; when God first tells him that Sarah will have a son, Abraham’s response is “O that Ishmael might live by Your favor!” (לוּ יִשְׁמָעֵאל יִחְיֶה לְפָנֶיךָ; Gen 17:18). In this sense, unlike what happens with Jacob, where his love for Rachel is transferred to her sons, and his lack of love for Leah colors his feelings about hers, Abraham seems quite attached to his oldest son, regardless of who his mother was.

Yet, while Abraham might not be described as hating Hagar, the narrator and later interpretations paint her in a most unfavorable light. In belittling Sarah (Gen 16:4), Hagar oversteps her bounds. Social norms dictate that Hagar should have remained subservient to Sarah both in her status as maidservant and as second-tier wife of the house. Consider too Seforno’s implicitly unfavorable description of Hagar (Gen 21:9); he suggests that Ishmael was parroting the disparaging remarks about Isaac that he had overheard his mother saying. Even without these rabbinic expansions, Hagar is certainly the lesser loved wife in the narrative, and her son naturally loses out to that of Abraham’s favorite wife, Sarah.

The Rights of the Firstborn Son of Any Wife

In light of this, I suggest that the case law in Deuteronomy 21 has both cases in mind, and relates to both forms of marriage known in the biblical world: polygyny and polycoity. The connection to the children of polygyny, Reuben and Joseph, is obvious. While the connection to the offspring of polycoity, Ishmael and Isaac, is subtler, nevertheless there appears to be little reason to read Deuteronomy as excluding it.

Moreover, as Carmichael notes, laws would not deal with such idiosyncratic features of a narrative such as the love of a specific father for the son of his less favored wife, but would abstract the principle.[29] The principle here is that the first issue of a man’s virility counts as the firstborn. Since secondary wives are wives, the principle of fairness to sons would seem to apply.

Deuteronomy Protects the Vulnerable



One of the hallmarks of Deuteronomy is the humane treatment of the weak and marginalized.[30] The sons of lesser loved wives, regardless of the marriage arrangement (polygyny or polycoity), would have been especially vulnerable to being mistreated. The reading suggested here keeps with the ethos of Deuteronomy, the potentially marginalized sons resulting from marriages to multiple women are protected by law.