Hebrews 5:1-6

For every high priest taken from among men is ordained for men in things pertaining to God, that he may offer both gifts and sacrifices for sins: who can have compassion on the ignorant, and on them that are out of the way; for that he himself also is compassed with infirmity. And by reason hereof he ought, as for the people, so also for himself, to offer for sins. And no man taketh this honour unto himself, but he that is called of God, as was Aaron. So also Christ glorified not himself to be made an high priest; but he that said unto him, Thou art my Son, To day have I begotten thee. As he saith also in another place, Thou art a priest for ever After the order of Melchisedec.