For those who may be interested in the full breadth of the Hebrews epistle,
herein linked to the full commentary while verses 26 thru 31 are pasted below.
The Book of Hebrews chapter 10
Introduction
The insufficiency of the legal sacrifices to take away sin, Hebrews 10:1-4. The purpose and will of God, as declared by the Psalmist, relative to the salvation of the world by the incarnation of Christ; and our sanctification through that will, Hebrews 10:5-10. Comparison between the priesthood of Christ and that of the Jews, Hebrews 10:11-14. The new covenant which God promised to make, and the blessings of it, Hebrews 10:15-17. The access which genuine believers have to the holiest by the blood of Jesus, Hebrews 10:18-20. Having a High Priest over the Church of God, we should have faith, walk uprightly, hold fast our profession, exhort and help each other, and maintain Christian communion, Hebrews 10:21-25. The danger and awful consequences of final apostasy, Hebrews 10:26-31. In order to our perseverance, we should often reflect on past mercies, and the support afforded us in temptations and afflictions; and not cast away our confidence, for we shall receive the promise if we patiently fulfill the will of God, Hebrews 10:32-37. The just by faith shall live; but the soul that draws back shall die, Hebrews 10:38. The apostle's confidence in the believing Hebrews, Hebrews 10:39.
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Verse 26
For if we sin wilfully - If we deliberately, for fear of persecution or from any other motive, renounce the profession of the Gospel and the Author of that Gospel, after having received the knowledge of the truth so as to be convinced that Jesus is the promised Messiah, and that he had sprinkled our hearts from an evil conscience; for such there remaineth no sacrifice for sins; for as the Jewish sacrifices are abolished, as appears by the declaration of God himself in the fortieth Psalm, and Jesus being now the only sacrifice which God will accept, those who reject him have none other; therefore their case must be utterly without remedy. This is the meaning of the apostle, and the case is that of a deliberate apostate - one who has utterly rejected Jesus Christ and his atonement, and renounced the whole Gospel system. It has nothing to do with backsliders in our common use of that term. A man may be overtaken in a fault, or he may deliberately go into sin, and yet neither renounce the Gospel, nor deny the Lord that bought him. His case is dreary and dangerous, but it is not hopeless; no case is hopeless but that of the deliberate apostate, who rejects the whole Gospel system, after having been saved by grace, or convinced of the truth of the Gospel. To him there remaineth no more sacrifice for sin; for there was but the One, Jesus, and this he has utterly rejected.
Verse 27
A certain fearful looking for of judgment - From this it is evident that God will pardon no man without a sacrifice for sin; for otherwise, as Dr. Macknight argues, it would not follow, from there remaining to apostates no more sacrifice for sin, that there must remain to them a dreadful expectation of judgment.
And fiery indignation - Και πυρος ζηλος· A zeal, or fervor of fire; something similar to the fire that came down from heaven and destroyed Korah and his company; Numbers 16:35.
Probably the apostle here refers to the case of the unbelieving Jews in general, as in chap. 6 to the dreadful judgment that was coming upon them, and the burning up their temple and city with fire. These people had, by the preaching of Christ and his apostles, received the knowledge of the truth. It was impossible that they could have witnessed his miracles and heard his doctrine without being convinced that he was the Messiah, and that their own system was at an end; but they rejected this only sacrifice at a time when God abolished their own: to that nation, therefore, there remained no other sacrifice for sin; therefore the dreadful judgment came, the fiery indignation was poured out, and they, as adversaries, were devoured by it.
Verse 28
He that despised Moses' law - Αθετησας· He that rejected it, threw it aside, and denied its Divine authority by presumptuous sinning, died without mercy - without any extenuation or mitigation of punishment; Numbers 15:30.
Under two or three witnesses - That is, when convicted by the testimony of two or three respectable witnesses. See Deuteronomy 17:6.
Verse 29
Of how much sorer punishment - Such offenses were trifling in comparison of this, and in justice the punishment should be proportioned to the offense.
Trodden under foot the Son of God - Treated him with the utmost contempt and blasphemy.
The blood of the covenant - an unholy thing - The blood of the covenant means here the sacrificial death of Christ, by which the new covenant between God and man was ratified, sealed, and confirmed. And counting this unholy, or common, κοινον, intimates that they expected nothing from it in a sacrificial or atoning way. How near to those persons, and how near to their destruction, do they come in the present day who reject the atoning blood, and say, "that they expect no more benefit from the blood of Christ than they do from that of a cow or a sheep!" Is not this precisely the crime of which the apostle speaks here, and to which he tells us God would show no mercy?
Despite unto the Spirit of grace? - Hath insulted the Spirit of grace. The apostle means the Holy Spirit, whose gifts were bestowed in the first age on believers for the confirmation of the Gospel. See Hebrews 6:4-6. Wherefore, if one apostatized in the first age, after having been witness to these miraculous gifts, much more after having possessed them himself, he must, like the scribes and Pharisees, have ascribed them to evil spirits; than which a greater indignity could not be done to the Spirit of God. Macknight. This is properly the sin against the Holy Ghost, which has no forgiveness.
Verse 30
Vengeance belongeth unto me - This is the saying of God, Deuteronomy 32:35, in reference to the idolatrous Gentiles, who were the enemies of his people; and is here with propriety applied to the above apostates, who, being enemies to God's ordinances, and Christ's ministry and merits, must also be enemies to Christ's people; and labor for the destruction of them, and the cause in which they are engaged.
The Lord shall judge his people - That is, he shall execute judgment for them; for this is evidently the sense in which the word is used in the place from which the apostle quotes, Deuteronomy 32:36; : For the Lord shall judge his people, and repent himself for his servants, when he seeth that their power is gone. So God will avenge and vindicate the cause of Christianity by destroying its enemies, as he did in the case of the Jewish people, whom he destroyed from being a nation, and made them a proverb of reproach and monuments of his wrathful indignation to the present day.
Verse 31
It is a fearful thing to fall into the hands of the living God - To fall into the hands of God is to fall under his displeasure; and he who lives for ever can punish for ever. How dreadful to have the displeasure of an eternal, almighty Being to rest on the soul for ever! Apostates, and all the persecutors and enemies of God's cause and people, may expect the heaviest judgments of an incensed Deity: and these, not for a time, but through eternity.