Genesis 26:8-11

8Now it came to pass, when he had been there a long time, that Abimelech king of the Philistines looked through a window, and saw, and there was Isaac, showing endearment to Rebekah his wife.

9Then Abimelech called Isaac and said, “Quite obviously she is your wife; so how could you say, ‘She is my sister’?” Isaac said to him, “Because I said, ‘Lest I die on account of her.’ ”

10And Abimelech said, “What is this you have done to us? One of the people might soon have lain with your wife, and you would have brought guilt on us.”

11So Abimelech charged all his people, saying, “He who touches this man or his wife shall surely be put to death.”