Genesis 26:8-10 (KJV)
8 And 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.
9 And 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 for her.
10 And Abimelech said, What is this thou hast done unto us? one of the people might lightly have lien with thy wife, and thou shouldest have brought guiltiness upon us.