Hebrews 7:8-10

Furthermore, here [in the Levitical priesthood] tithes are received by men who are subject to death; but in that case [concerning Melchizedek], they are received by one of whom it is testified that he lives on [perpetually]. A person might even say that Levi [the father of the priestly tribe] himself, who received tithes, paid tithes through Abraham [the father of all Israel and of all who believe], for Levi was still in the loins (unborn) of his forefather [Abraham] when Melchizedek met him (Abraham).