Genesis 26:7-9

7When the men who lived there asked Isaac about his wife, Rebekah, he said, “She is my sister.” He was afraid to say, “She is my wife.” He thought, “They will kill me to get her, because she is so beautiful.”

8But some time later, Abimelech, king of the Philistines, looked out his window and saw Isaac caressing Rebekah.

9Immediately, Abimelech called for Isaac and exclaimed, “She is obviously your wife! Why did you say, ‘She is my sister’?” “Because I was afraid someone would kill me to get her from me,” Isaac replied.