The chapter’s original character, however, can be uncovered with a little detective work.

The core of Leviticus 18 is the list of incest laws, each of which includes the memorable phrase “uncover nakedness.” This is typically understood as a euphemism for sexual intercourse, so “you shall not uncover the nakedness of your father’s sister” would mean something like “do not have sex with your father’s sister.”

Most of the incest laws are presented in a straightforward manner, but two are not. The first exception is: “The nakedness of your father and the nakedness of your mother you shall not uncover; she is your mother, you shall not uncover her nakedness” (emphasis mine). At first, this verse appears to outlaw sex between a man and either of his parents. However, the italicized explanation, or gloss, suggests that the law actually addresses only one parent: the mother. It is difficult to reconcile the two parts of this sentence.

The same thing happens again a few verses later: “You shall not uncover the nakedness of your father’s brother.” Simple enough, right? The following gloss, however, may give you whiplash: “you shall not approach his wife, she is your aunt.” By the time we’ve finished reading the gloss, a prohibition against intercourse between a man and his paternal uncle has transformed into a law about sex between a man and that uncle’s wife.

Each verse in Leviticus 18’s series of incest laws contains a similar gloss, but the others are merely emphatic, driving home the point. (For example, “You shall not uncover the nakedness of your daughter-in-law; she is your son’s wife, you shall not uncover her nakedness.”) Only in these two cases — the father and mother, and the father’s brother — do the glosses alter our understanding of what is prohibited. A law prohibiting sex with one’s father fades away, and a law against sex with one’s uncle is reinterpreted as a ban on sex with one’s aunt.

What we have here is strong evidence of editorial intervention.

It is worth noting that these new glosses render the idiom “uncover nakedness” incoherent. The phrase can no longer denote sex if uncovering the nakedness of one’s father is an act that also involves one’s mother — as the gloss implies.