Hebrews 7:6-8

But Melchizedek, who was not a descendant of Levi, collected a tenth from Abraham. And Melchizedek placed a blessing upon Abraham, the one who had already received the promises of God. And without question, the person who has the power to give a blessing is greater than the one who is blessed. The priests who collect tithes are men who die, so Melchizedek is greater than they are, because we are told that he lives on.