Genesis 26:6-10

So Isaac lived in Gerar.

When the men of the place asked about his wife, 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 beautiful.”

Now it came about, when he had been there a long time, that Abimelech king of the Philistines looked down through a window, and saw them, and behold, Isaac was caressing his wife Rebekah.

Then Abimelech called Isaac and said, “Behold, she certainly is your wife! So how is it that you said, ‘She is my sister’?” And Isaac said to him, “Because I thought, ‘otherwise I might be killed on account of her.’ ”

And Abimelech said, “What is this that you have done to us? One of the people might easily have slept with your wife, and you would have brought guilt upon us.”