Genesis 42:3-8

And Joseph's ten brethren went down to buy corn in Egypt. But Benjamin, Joseph's brother, Jacob sent not with his brethren; for he said, Lest peradventure mischief befall him. And the sons of Israel came to buy corn among those that came: for the famine was in the land of Canaan. And Joseph was the governor over the land, and he it was that sold to all the people of the land: and Joseph's brethren came, and bowed down themselves before him with their faces to the earth. And Joseph saw his brethren, and he knew them, but made himself strange unto them, and spake roughly unto them; and he said unto them, Whence come ye? And they said, From the land of Canaan to buy food. And Joseph knew his brethren, but they knew not him.