Genesis 20:11-13

11Abraham said, "I did it because I thought, 'There is no fear of God at all in this place, and they will kill me because of my wife.'

12Besides, she is indeed my sister, the daughter of my father though not the daughter of my mother, and she became my wife.

13And when God caused me to wander from my father's house, I said to her, 'This is the kindness you must do me: at every place to which we come, say of me, "He is my brother."'"