Heb 5:5, 8-10, Heb 7:14-17, 20-21, 27

In the Old Testament, Aaron's grandson Phinehas saved the Israelites from God's wrath. So God gave Phinehas and his descendants the office of priests forever. (Numbers 25:13)

Numbers 25:13 And he shall have it, and his seed after him, even the covenant of an everlasting priesthood; because he was zealous for his God, and made an atonement for the children of Israel.

As a tribe of Judah, Jesus became high priest in the order of Melchizedek. And even though Jesus was the Son of God, he offered himself up to God and accomplished the work of a high priest forever. (Heb 5:5-10, Heb 7:14-21,27)

Heb 5:5 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. 6 As he saith also in another place, Thou art a priest for ever after the order of Melchisedec. 7 Who in the days of his flesh, when he had offered up prayers and supplications with strong crying and tears unto him that was able to save him from death, and was heard in that he feared; 8 Though he were a Son, yet learned he obedience by the things which he suffered; 9 And being made perfect, he became the author of eternal salvation unto all them that obey him; 10 Called of God an high priest after the order of Melchisedec.

Heb 7:14 For it is evident that our Lord sprang out of Juda; of which tribe Moses spake nothing concerning priesthood. 15 And it is yet far more evident: for that after the similitude of Melchisedec there ariseth another priest, 16 Who is made, not after the law of a carnal commandment, but after the power of an endless life. 17 For he testifieth, Thou art a priest for ever after the order of Melchisedec. 18 For there is verily a disannulling of the commandment going before for the weakness and unprofitableness thereof. 19 For the law made nothing perfect, but the bringing in of a better hope did; by the which we draw nigh unto God. 20 And inasmuch as not without an oath he was made priest: 21 (For those priests were made without an oath; but this with an oath by him that said unto him, The Lord sware and will not repent, Thou art a priest for ever after the order of Melchisedec:) 27 Who needeth not daily, as those high priests, to offer up sacrifice, first for his own sins, and then for the people's: for this he did once, when he offered up himself.