Question about Hebrews 10:26

To deny Christ the way Peter did in the course of one evening, is not to blaspheme against the Holy Spirit, which is the one unforgivable sin. Jesus made that very clear when he said that whoever speaks against himself will be forgiven, but not if there is blasphemy against the Holy Spirit. Knowing Peter would renounce him, Jesus had prayed in advance that Satan would not have him, but that Peter's faith would not fail, "and when thou art converted, strengthen thy brethren" (Luke 22:31-34). Jesus previously had said:

"All sins shall be forgiven unto the sons of men, and blasphemies wherewith soever they shall blaspheme. But he that shall blaspheme against the Holy Spirit hath never forgiveness, but is in danger of eternal damnation." (Mark 3:28-29)

That is why, when Peter broke down in tears, realising he had disowned Christ, he was repentant, and so he was forgiven. Yet if his denial of knowing Christ had constituted the one unforgivable sin, he would not have been restored. The very fact that there are not two, or three, or more unforgivable sins means that it is only that one particular sin that brings furious judgment and consuming fire for the one who blasphemes against the Holy Spirit.

This clearly indicates that to go on deliberately sinning despite knowing one is willfully continuing to sin, means that - at some point known only to God - there can be no application of Christ's sacrifice for sins. It does not mean that one had been forgiven, then that forgiveness is withdrawn. Notice how the person has a knowledge of the matter? Yet to know the truth about sin and forgiveness does not necessarily mean a person has truly repented, put faith in that provision of Christ, and has been saved. They know about all of that. Which is why their rejection of that gracious provision means it will never be applied to them.

There are many Christians who have fallen into sin after experiencing a cleansed conscience and acceptance in Christ - Peter, for example - but when it is not deliberate and continued sin, they repent and are restored. Once more their conscience is cleansed as they experience fresh forgiveness. They have not blasphemed against the Holy Spirit.

The problem with this whole matter is that people like to judge whether a professed Christian truly was saved, so that if that person is seen to fall into serious sin thereafter, they can point to that as "proof" that the "once saved, always saved" notion they sarcastically level against some groups is wrong. Other groups use uncertainty about salvation, lack of assurance about being saved, as a kind of spiritual stick to urge members on, while holding out the "carrot" of eventual salvation (if they keep doing all the things their group says they must do to merit salvation). However, those who have been saved by grace, and not due to anything they have done, rest in the finished work of Christ, while getting on with pointing Christ to others, sharing the good news of Christ, and living upright lives, as all Christians should. When they do sin (as all Christians do) they repent and are forgiven by God. But some who never did experience saving grace (only knowing about it), could become lax (antinomianism is a term that may apply) and risk continuing, deliberate sin, for which there comes a point where forgiveness of sins will never be applied to them.

It does not mean that one can no longer be saved, but it does demonstrate the falsity of the claim that we are "once saved, always saved," since Paul here outlines a way in which those "once saved" might later be damned.

As for how you can respond to this biblically, there are many passages in the Gospels that show someone who once was in the kingdom, left, and returned only to be welcomed. The parable of the prodigal son (Luke 15) is one such example. The prodigal son already is in his father's house. He already knows the truth and has a claim to the inheritance. He takes that inheritance and spends it foolishly, until his is completely broke and without any goodness. Then, he repents and returns and is welcomed back.

The narrative involving Peter denying Christ and then repenting is also an example of this. Surely, Peter already had the truth before denying Christ. Scripture makes this very clear. Yet he denied Him anyway. But, when he repented, Christ forgave him and welcomed him backed.

Jesus also says you should not forgive your brother 7 times, but seven times seventy (Matt 18:21-22). Essentially, this means that you must forgive your brother as often as he repents of his sins. God does the same for us.