Genesis 26:7-9

When the men of that place asked him about his wife, he said, “She is my sister,” because he was afraid to say, “She is my wife.” He thought, “The men of this place might kill me on account of Rebekah, because she is beautiful.” When Isaac had been there a long time, Abimelek king of the Philistines looked down from a window and saw Isaac caressing his wife Rebekah. So Abimelek summoned Isaac and said, “She is really your wife! Why did you say, ‘She is my sister’?” Isaac answered him, “Because I thought I might lose my life on account of her.”