Genesis 26:7-10

7and the men of the place asked him of his wife; and he said, She is my sister: for he feared to say, My wife; lest, said he, the men of the place should kill me for Rebekah; because she was fair to look upon.

8And it came to pass, when he had been there a long time, that Abimelech king of the Philistines looked out at a window, and saw, and, behold, Isaac was sporting with Rebekah his wife.

9And Abimelech called Isaac, and said, Behold, of a surety she is thy wife: and how saidst thou, She is my sister? And Isaac said unto him, Because I said, Lest I die because of her.

10And Abimelech said, What is this thou hast done unto us? one of the people might easily have lain with thy wife, and thou wouldest have brought guiltiness upon us.