Check out this fascinating article which shows what Book of Mormon prophets thought of polygamy and also why polygamy was practiced in the early days of the Church.

Not long after the early Nephites established themselves in the New World, the prophet Jacob felt compelled to condemn the wickedness he saw in their burgeoning society. Jacob delivered a condemnatory speech at the temple where he chastised the Nephites for their “wickedness and abominations” (Jacob 2:10), specifically their pride (Jacob 2:13, 16, 20, 22), materialism (Jacob 2:13, 17–19), and sexual immorality (Jacob 2:23–35).

Concerning their “whoredoms” (Jacob 2:23, 28, 33), Jacob specifically mentioned unauthorized polygamy as an iniquitous practice. “Behold, David and Solomon truly had many wives and concubines, which thing was abominable before me, saith the Lord. . . . Wherefore, I the Lord God will not suffer that this people shall do like unto them of old” (Jacob 2:24, 26). Jacob therefore categorized such unauthorized instances of polygyny and concubinage (a man marrying multiple women), as sinful, for, he said, God “delight[s] in the chastity of women” (Jacob 2:28), and would not tolerate lascivious men abusing women (Jacob 2:32–33).

That being the general rule, Jacob went on to qualify that law, saying that plural marriage is justifiable but only when God commands it. “Wherefore, this people shall keep my commandments, saith the Lord of Hosts, or cursed be the land for their sakes. For if I will, saith the Lord of Hosts, raise up seed unto me, I will command my people; otherwise they shall hearken unto these things” (Jacob 2:29–30). As Latter-day Saint researcher Brian Hales commented, “The Nephite prophet Jacob reiterates a commandment given to his father Lehi establishing monogamy as the rule and polygamy as only a divinely commanded exception.”

Images from Book of Mormon Central.