Abraham deceived Abimelech, the king of Gerar, into thinking Sarah was just Abraham's sister. So naturally, Abimelech took Sarah as his wife. But wait! Didn't God just tell Abraham and Sarah they would have a child within the year? But now Sarah is another man's wife and we have a serious problem on our hands.
Sources:
Armstrong, S. (2012b, January 8). Genesis 2011 - Lesson 20. Verse By Verse Ministry International. https://versebyverseministry.org/lessons/genesis_2011_lesson_20
Guzik, D. (2018b). Study Guide for Genesis 20. Blue Letter Bible. https://www.blueletterbible.org/comm/guzik_david/study-guide/genesis/genesis-20.cfm
