Hebrews 7:9-12

ISV(i) 9 One might even say that Levi, who collects the tenth, paid the tenth through Abraham, 10 because Levi was still inside his ancestor when Melchizedek met him.
11 Now if perfection could have been attained through the Levitical priesthood—for on this basis the people received the Law—what further need would there be to speak of appointing another kind of priest according to the order of Melchizedek, not one according to the order of Aaron? 12 When a change in the priesthood takes place, there must also be a change in the Law.