Genesis 20:9-12

9Then Abimelech called Abraham and said to him, "What have you done to us? And how have I sinned against you, that you have brought on me and my kingdom a great sin? You have done to me things that ought not to be done."

10And Abimelech said to Abraham, "What did you see, that you did this thing?"

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.