Hebrews 5:1, 3, 6, 10, 12

For every high priest taken from among men is appointed on behalf of men in things pertaining to God, in order to offer both gifts and sacrifices for sins

and because of it he is obligated to offer sacrifices for sins, as for the people, so also for himself.

just as He says also in another passage, “YOU ARE A PRIEST FOREVER ACCORDING TO THE ORDER OF MELCHIZEDEK.”

being designated by God as a high priest according to the order of Melchizedek.

For though by this time you ought to be teachers, you have need again for someone to teach you the elementary principles of the oracles of God, and you have come to need milk and not solid food.