Problem: Because Sarai was barren, she told Abraham to impregnate her handmaiden, Hagar. However, this seems too bizarre to be believed! Why would Sarai willingly tell her husband to cheat on her?
Solution: This was actually a common practice in the ancient Near East. In fact, women often signed prenuptial agreements to do this in the event that they could not bear children. Hoffmeier writes, “Some ancient Mesopotamian marriage contracts actually include a prenuptial agreement that if a woman did not bear children, it was her obligation to furnish a surrogate for her husband.” In fact, the Code of Hammurabi (170-171) had similar instructions for children born to a handmaiden, rather than the wife.
 Hoffmeier, James Karl. The Archaeology of the Bible. Oxford: Lion, 2008. 44.
“Now Sarai Abram’s wife bare him no children: and she had an handmaid, an Egyptian, whose name was Hagar.And Sarai said unto Abram, Behold now, the Lord hath restrained me from bearing: I pray thee, go in unto my maid; it may be that I may obtain children by her. And Abram hearkened to the voice of Sarai.