Whereof the Holy Ghost is a witness to us - That is, the Holy Spirit is a proof of the truth of the position here laid down - that the one atonement made by the Redeemer lays the foundation for the eternal perfection of all who are sanctified. The witness of the Holy Spirit here referred to is what is furnished in the Scriptures, and not any witness in ourselves. Paul immediately makes his appeal to a passage of the Old Testament, and he thus shows his firm conviction that the Scriptures were inspired by the Holy Spirit.
For after that he had said before - The apostle here appeals to a passage which he had before quoted from Jeremiah 31:33-34; see it explained in the notes on Hebrews 8:8-12. The object of the quotation in both cases is, to show that the new covenant contemplated the formation of a holy character or a holy people. It was not to set apart a people who should be externally holy only, or be distinguished for conformity to external rites and ceremonies, but who should be holy in heart and in life. There has been some difficulty felt by expositors in ascertaining what corresponds to the expression “after that he had said before,” and some have supposed that the phrase “then he saith” should be understood before Hebrews 10:17. But probably the apostle means to refer to two distinct parts of the quotation from Jeremiah, the former of which expresses the fact that God meant to make a new covenant with his people, and the latter expresses the nature of that covenant, and it is particularly to the latter that he refers. This is seen more distinctly in the passage in Jeremiah than it is in our translation of the quotation in this Epistle. The meaning is this, “The Holy Spirit first said, this is the covenant that I will make with them:” and having said this, he then added, “After those days, I will put my laws into their hearts, and in their minds will I write them, and their sins and their iniquities will I remember no more.” The first part of it expresses the purpose to form such a covenant; the latter states what that covenant would be. The quotation is not, indeed, literally made, but the sense is retained; compare the notes on Hebrews 8:8-12. Still, it may be asked, how this quotation proves the point for which it is adduced - that the design of the atonement of Christ was “to perfect forever them that are sanctified?” In regard to this, we may observe:
(1)That it was declared that those who were interested in it would be holy, for the law would be in their hearts and written on their minds; and,
(2)That this would be “entire and perpetual.” Their sins would be “wholly” forgiven; they would never be remembered again - and thus they would be “perfected forever.”