Genesis 26:8-10

But some time later, Abimelech, king of the Philistines, looked out his window and saw Isaac caressing Rebekah. Immediately, 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. “How could you do this to us?” Abimelech exclaimed. “One of my people might easily have taken your wife and slept with her, and you would have made us guilty of great sin.”