Genesis 20:10-13

10Abimelech also asked Abraham, “What prompted you to do such a thing?”

11Abraham replied, “I thought to myself, ‘Surely there is no fear of God in this place. They will kill me on account of my wife.’ 12Besides, she really is my sister, the daughter of my father—though not the daughter of my mother—and she became my wife. 13So when God had me journey from my father’s house, I said to Sarah, ‘This is how you can show your loyalty to me: Wherever we go, say of me, “He is my brother.”’”