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: therefore it shall come to pass, when the Egyptians shall see thee, that they shall 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 my soul shall live because of thee.