Genesis 26:7-8

26:7 When the men of that place asked him about his wife, he replied, “She is my sister.” He was afraid to say, “She is my wife,” for he thought to himself, “The men of this place will kill me to get Rebekah because she is very beautiful.”

26:8 After Isaac had been there a long time, Abimelech king of the Philistines happened to look out a window and observed Isaac caressing his wife Rebekah.