This is commonly interpreted to be talking about the person who knows about salvation, but has not actually gotten saved. But it plainly talks about the impossibility of being renewed to repentance
AGAIN. Once you repent and become a partaker of the Holy Spirit and you then fall away it is impossible for you to come back to repentance. God does not allow it because it puts Christ to open shame. God is not mocked. He doesn't let people play games with the blood. He does not allow it to be trampled.
Note how barren fields are burned in the end,
not saved as some Christians insist their barren field will be. (A barren field is nothing more than James' 'faith without works' in James 2--the faith that can not save, he says.) They think they will be saved because they reason that salvation happens first, at the beginning of believing, which it surely does, and so nothing can have any affect on what has already transpired.
The problem is they do not know the whole counsel of scripture that warns us that we have to continue to be believing to continue to be saved, and that if you remain a barren field right up to the Day of Judgment you will be showing yourself to either 1) never truly believed to begin with and so you never received the Holy Spirit to create holy works in you, or 2) you stopped believing somewhere along the line and no longer have the Holy Spirit inside of you to create holy works in you. Either way, if you get to the Judgment as a barren, fruitless field, you will be burned, not saved.
Yes, 'things that accompany salvation'. And he says what it is that accompanies salvation. Yet there are so many people who insist there is nothing that must accompany salvation. The author just got through saying if you don't have anything accompanying your salvation
you will be burned, not saved.
Notice what inherits the promises: faith and patience (the perseverance of faith). Yet so many Christians are sure you do not have to keep patiently believing to the end to inherit the promises.
The author is beginning a long treatise about the supremacy of Christ's ministry over and above the ministry of the earthly Levites. See, the ministry of the priest is only as effective as the ability of the priest himself. We see in the old covenant that if the priest failed in his duties, or ceased to live to continue to perform his duties, the worshiper whom he represents could not have the relationship with the Father that the priest was working to get for them.
But since Christ has none of these limitations we can approach the Father in full assurance of faith knowing that our faith is well placed in Christ and he will never let us down, he will never fail in his duties, he will never lose those who God gives to him to minister on behalf of. His ministry is perfect and indestructible.
The author wraps up these chapters of how perfect and incorruptible Christ's ministry with that very exhortation: Christ can never fail. He will represent you perfectly and secure for you the relationship with the Father you need to be saved.
"19Therefore, brethren, since we have confidence to enter the holy place by the blood of Jesus,20by a new and living way which He inaugurated for us through the veil, that is, His flesh, 21and since we have a great priest over the house of God, 22let us draw near with a sincere heart in full assurance of faith, having our hearts sprinkled clean from an evil conscience and our bodies washed with pure water. 23Let us hold fast the confession of our hope without wavering, for He who promised is faithful;" (Hebrews 10:19-23 NASB)
The problem is, the church has viewed the perfection and all sufficiency of Christ's ministry to mean they are saved no matter what. It's gotten to the point now in the church that even believing is not necessary to 'do' after you first receive Christ. But if you read above, what Christ's perfect ministry means is it is worthy of your faith. Your faith is well placed and not in vain when it is in Christ because "He who promised is faithful" (vs. 23 above), so keep believing!
Can you see these two distinct ways of interpreting the meaning and application of Christ's perfect ministry? One way says, "nothing matters once you are saved because Christ's ministry is perfect and does it all." The other (correct) way says, "Christ's ministry is perfect and can do exactly what it must do for me,
therefore I will, and must continue to rely on it".