Genesis 12:10-13

And there was a famine in the land: and Abram went down into Egypt to sojourn there; for the famine was sore in the land. And it came to pass, when he was come near to enter into Egypt, that he said unto Sarai his wife, Behold now, I know that thou art a fair woman to look upon: and it will come to pass, when the Egyptians shall see thee, that they will say, This is his wife: and they will kill me, but they will save thee alive. Say, I pray thee, thou art my sister; that it may be well with me for thy sake, and that my soul may live because of thee.