Genesis 26:7-9

When the men of the place asked him about his wife, he said, “She is my sister,” for he feared to say, “My wife,” thinking, “lest the men of the place should kill me because of Rebekah,” because she was attractive in appearance. When he had been there a long time, Abimelech king of the Philistines looked out of a window and saw Isaac laughing with Rebekah his wife. So Abimelech called Isaac and said, “Behold, she is your wife. How then could you say, ‘She is my sister’?” Isaac said to him, “Because I thought, ‘Lest I die because of her.’”