Genesis 47:22-26

47:22 But he did not purchase the land of the priests because the priests had an allotment from Pharaoh and they ate from their allotment that Pharaoh gave them. That is why they did not sell their land.

47:23 Joseph said to the people, “Since I have bought you and your land today for Pharaoh, here is seed for you. Cultivate the land. 47:24 When you gather in the crop, give one-fifth of it to Pharaoh, and the rest will be yours for seed for the fields and for you to eat, including those in your households and your little children.” 47:25 They replied, “You have saved our lives! You are showing us favor, and we will be Pharaoh’s slaves.”

47:26 So Joseph made it a statute, which is in effect to this day throughout the land of Egypt: One-fifth belongs to Pharaoh. Only the land of the priests did not become Pharaoh’s.