[quoting from Charles Stanley (1821-1890)
on Hebrews 10]
"Now what was the will of God? Is it not revealed in what follows, that we should be sanctified, separated unto God, by the offering of the body of Christ? “By the which will we are sanctified, through the offering of the body of Jesus Christ once.”
Note, it was not the will of God to set up another system of many offerings, or masses, but one offering, offered once. It is then a great foundation truth, a fact,
that through the one offering of Christ, once offered, we ARE sanctified. Do you believe God as to this? or do you say, No, that one offering is not enough to separate me forever to God? Beware of unbelief as to this.
[...]
"Here in Hebrews, it is the question of the conscience: and by the one offering of Christ the believer has no more conscience of sins. The Holy Spirit is a witness that God has nothing now against the believer, as He says, “And their sins and iniquities will I remember no more.” Oh, the holy boldness, or liberty we have to enter the holiest by the blood of Jesus. Now the one question is, Do we believe God? You must admit that it is altogether of God. Do not send out the spies of unbelieving reason, to see if it is so. Do not look within to see if it is so. The Holy Spirit bears witness that He who died on the cross, as the sacrifice for your sins, has perfected us forever -in unchanging continuance. Christendom does not believe the Holy Spirit. All her printed prayers show that men do not believe this wondrous grace of God. Ever using vain repetitions for God to be merciful, when He declares in the plainest words of all believers, “Their sins and iniquities will I remember no more!” If you believe God, you must have done with masses and vain repetitions. It is a serious thing to say, We are Jews, when we are not; to set up an earthly priesthood again, and to repeat prayers only suited for a Jew before Christ died.
"
If Christ by His one sacrifice has settled the whole question of our sins, perfectly or completely to the glory of God, then plainly there is no more offering for sin.
To offer sacrifices now for the sins of the living and the dead, is the most distinct denial of Christianity, be this by whom it may.
But if while protesting against such a human priesthood and vain unscriptural sacrifices, in the pretended offering up of Christ on human devised altars,
we ourselves disbelieve the testimony of God to the one sacrifice of Christ, what better off are we than they?"
--Charles Stanley [1821-1890], Hebrews 10
https://bibletruthpublishers.com/hebrews-10/charles-stanley/pamphlets/c-stanley/la61566
[end quoting; bold and underline mine]
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We must also keep in mind the CONTEXT of "Hebrews"