Genesis 12:11-13

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.