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:) 22: By so much was Jesus made a surety of a better testament. 23: And they truly were many priests, because they were not suffered to continue by reason of death: 24: But this man, because he continueth ever, hath an unchangeable priesthood. 25: Wherefore he is able also to save them to the uttermost that come unto God by him, seeing he ever liveth to make intercession for them. 26: For such an high priest became us, who is holy, harmless, undefiled, separate from sinners, and made higher than the heavens; 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. 28: For the law maketh men high priests which have infirmity; but the word of the oath, which was since the law, maketh the Son, who is consecrated for evermore.
So Christ has been raised up a priest, not like the Aaronic priests, but like Melchisedec the priest, whose priesthood is not according to the law of commandments to feeble human life but in the empowering of God to an endless life. The commandment of the Law had to be disannulled because it was weak and unprofitable. The Mosaic Law did not bring salvation to anyone but the bringing in of a better hope, did bring salvation. And it is to this hope found in the person of Christ that is offered to you. The Aaronic priests were not ordained by an oath, but Christ is ordained by an oath. The LORD swore and will never change his mind. Christ is a priest after the order of Melchisedec. Therefore Jesus is made a surety (A person who guarantees future blessing) of a better testament (Covenant). Christ Jesus is the guarantor of the New Covenant. The old priests ministry ended in death but Christ’s ministry continues forever and his priesthood in unchangeable. Therefore he is able to save to the uttermost (right on to the end) those who come to him, because he ever lives to make intercession for them. We have a high priest who is holy, harmless, undefiled, separate from sinners, made higher than the heavens. His ministry is not like the priests of old who daily offered a sacrifice first for their own sins and then for the people. Christ only offered one sacrifice for sin when he placed himself upon the altar. (There was no sacrifice necessary for him because he was without sin) The Law ordained man with human limitations but the Word of the Lord in the form of an oath made Christ the Son of God, Priest forevermore.