Deuteronomy 17:14–17: Many Wives and the King's Heart
Deuteronomy 17:14–17 addresses the king of Israel, not every household, and it forbids multiplying wives for a stated reason: they could turn his heart away. The text treats many wives as a royal danger to covenant loyalty rather than an ideal.
Genesis 2:24: One Flesh and Plural Marriage
Genesis 2:24 sets the shape of marriage before sin enters the story: one man, one wife, one new bond. The verse never uses the word sin, so the case against plural marriage rests on this design read alongside the rest of Scripture.