Genesis 26:7-9

The men of the place asked him about his wife, and he said, “She is my sister,” for he was afraid to say, “my wife”—thinking, “the men of the place might kill me on account of Rebekah, since she is very beautiful.” It happened when he had been there a long time, that Abimelech king of the Philistines looked out of a window and saw Isaac caressing Rebekah his wife. Then Abimelech called Isaac and said, “See here, Rebekah is in fact your wife! How did you [dare to] say to me, ‘She is my sister’?” And Isaac said to him, “Because I thought I might be killed because of her [desirability].”