17 for He doth testify—'Thou 'art' a priest—to the age, according to the order of Melchisedek;' 18 for a disannulling indeed doth come of the command going before because of its weakness, and unprofitableness, 19 (for nothing did the law perfect) and the bringing in of a better hope, through which we draw nigh to God. 20 And inasmuch as 'it is' not apart from oath, (for those indeed apart from oath are become priests, 21 and he with an oath through Him who is saying unto him, 'The Lord sware, and will not repent, Thou 'art' a priest—to the age, according to the order of Melchisedek;')
Matthew Henry's Commentary on Hebrews 7:17-21
Commentary on Hebrews 7:11-25
(Read Hebrews 7:11-25)
The priesthood and law by which perfection could not come, are done away; a Priest is risen, and a dispensation now set up, by which true believers may be made perfect. That there is such a change is plain. The law which made the Levitical priesthood, showed that the priests were frail, dying creatures, not able to save their own lives, much less could they save the souls of those who came to them. But the High Priest of our profession holds his office by the power of endless life in himself; not only to keep himself alive, but to give spiritual and eternal life to all who rely upon his sacrifice and intercession. The better covenant, of which Jesus was the Surety, is not here contrasted with the covenant of works, by which every transgressor is shut up under the curse. It is distinguished from the Sinai covenant with Israel, and the legal dispensation under which the church so long remained. The better covenant brought the church and every believer into clearer light, more perfect liberty, and more abundant privileges. In the order of Aaron there was a multitude of priests, of high priests one after another; but in the priesthood of Christ there is only one and the same. This is the believer's safety and happiness, that this everlasting High Priest is able to save to the uttermost, in all times, in all cases. Surely then it becomes us to desire a spirituality and holiness, as much beyond those of the Old Testament believers, as our advantages exceed theirs.