Genesis 47:23-26

23Then Joseph said to the people, "Behold, I have this day bought you and your land for Pharaoh. Now here is seed for you, and you shall sow the land.

24And at the harvests you shall give a fifth to Pharaoh, and four fifths shall be your own, as seed for the field and as food for yourselves and your households, and as food for your little ones."

25And they said, "You have saved our lives; may it please my lord, we will be servants to Pharaoh."

26So Joseph made it a statute concerning the land of Egypt, and it stands to this day, that Pharaoh should have the fifth; the land of the priests alone did not become Pharaoh's.