Commentaries:
How long did God forbear with converted Abraham? We are talking about the "father of the faithful"! Verse 17 takes place after everything was all cleared up between him and Abimelech.
How long did it take them to notice that all the women in Abimelech's house were barren? At least a couple months. God did not strike him down for his lie. He gave Abraham a chance to repent, to confess both to God and Abimelech what the truth was, but he never did it. So finally God stepped in, giving Abimelech a dream that told him he was keeping His prophet's wife, and he had better give her back.
Notice God's forbearance. Not only did He do this over a long time, but He kept Abimelech from defiling Sarah. He also kept Abimelech from killing Abraham for lying to the king. God worked everything out. It could have been an awful situation. Isaac might never have lived, because Isaac is not born until the next chapter. God also shows His forbearance with Sarah - call her "the mother of the faithful" - because she was in on the lie. Yet, she is mentioned in Hebrews 11 as one of the heroes of faith.
Perhaps the most astounding fact is that this was the second time that it had happened! Genesis 12:10-20 records that the same thing occurred between Abraham and Pharaoh fifteen or twenty years earlier. How long did God forbear with Abraham? Fifteen or twenty years! He had given Abraham a couple of decades to repent of this sin, but he did not do it - so God tested him again. Eventually, Abraham did repent, but there was a fifteen- or twenty-year period in which God forbore with him in this problem to help him grow in character.
Richard T. Ritenbaugh
Forbearance