Genesis 20:7

Now, therefore, restore the man his wife; for he is a prophet, and he shall pray for thee, and thou shalt live; and if thou restore her not, know that thou shalt surely die, thou and all that are thine. If, after this revelation, Abimelech had persisted in keeping Sarah, his sin would have been one of malice, and death would have been the certain retribution, not only his own death, but that of his whole family. By telling Abimelech that he would remain alive only by virtue of the intercession of Abraham, who was one of His own prophets, the Lord showed that He knew the king to be capable of true moral understanding. It is a wise person that permits himself to be governed by God's directions after some stumble or mistake.