Genesis 47:23-26

23Then Joseph said to the people, “Now that I have acquired you and your land for Pharaoh this day, here is seed for you to sow in the land. 24At harvest time, you are to give a fifth of it to Pharaoh, and four-fifths will be yours as seed for the field and food for yourselves and your households and children.”

25“You have saved our lives,” they said. “We have found favor in our lord’s eyes, and we will be Pharaoh’s servants.” 26So Joseph established a law that a fifth of the produce belongs to Pharaoh, and it is in effect in the land of Egypt to this day. Only the priests’ land does not belong to Pharaoh.