In the Book of Genesis, when Adam sees Eve, he immediately says “This is now bone of my bones and flesh of my flesh” (Genesis 2:23). The narrator adds, “Therefore shall a man leave his father and his mother and shall cleave unto his wife; and they shall be one flesh” (Genesis 2:24). In this statement, Genesis gives religious sanction to the monogamous nuclear family.
Although this form of family has endured to modern times, and shows no sign of disappearing despite divorces, remarriages and blended families, it is not the only possible form of marriage. In fact, it is not the only kind of marriage known in the biblical world, for both the patriarchs and the kings of Israel had more than one wife. The announcement of the monogamous family in Genesis and the projection of its origin to the very beginning of humanity, was a revolutionary rather than a conservative act.
Israel did not invent the monogamous family, but it did consider it the central human mating form, and its laws of marriage seek to preserve it. Prime among these laws are the laws against adultery.