Genesis 20:1 From there Abraham journeyed toward the territory of the Negeb and lived between Kadesh and Shur; and he sojourned in Gerar. 2 And Abraham said of Sarah his wife, “She is my sister.” And Abimelech king of Gerar sent and took Sarah. 3 But God came to Abimelech in a dream by night and said to him, “Behold, you are a dead man because of the woman whom you have taken, for she is a man's wife.” 4 Now Abimelech had not approached her. So he said, “Lord, will you kill an innocent people? 5 Did he not himself say to me, ‘She is my sister’? And she herself said, ‘He is my brother.’ In the integrity of my heart and the innocence of my hands I have done this.” 6 Then God said to him in the dream, “Yes, I know that you have done this in the integrity of your heart, and it was I who kept you from sinning against me. Therefore I did not let you touch her. 7 Now then, return the man's wife, for he is a prophet, so that he will pray for you, and you shall live. But if you do not return her, know that you shall surely die, you and all who are yours.”
This is one of those passages where we look at the actions of one of God's people and shake our heads, until we look in the mirror. Thankfully God does intervene often to defend others from our stupidity (and us from others'.) God said to Abimelech: "You really don't want to go there; you don't what to do that." Abimelech humbly received God's warning, and so should we.