Will the Lord have me even if I ask: encouragement and candor for worried souls
One of the most common things people worry about when they begin to seriously consider Christianity for the first time (or, as in my case, to take Christ seriously after living for a long time in obvious defiance of Him while claiming to be Christians) is whether the warnings in Scripture about things like high-handed sins (Numbers 15:27-31), blasphemy against the Holy Spirit (Matthew 12:30-37), and apostasy (Hebrews 6:1-8, Hebrews 10:19-39) mean that it is impossible for them to be saved regardless of whether they repent and believe the Gospel. I lived in that fear for 3 years before laying hold of anything like peace of mind about it, but I do not think the Lord wasted even those years. More and more, I am convinced that He meant to drive me to a deeper study of His written word and the contexts which surround it (such as the history of the Church and the sorts of minds the original readers of Scripture would have had) and then to share the benefits of those studies with others who have similar fears.
Lest I give the wrong impression, I'm not saying that no one ought to have those fears. I'd love to say that, but to do so would be to accuse the Lord of having included things in Scripture which serve no other purpose than to create false fears in those who believe in Him. The Bible is, after all, primarily written for the sake of God's people, not primarily for the sake of those who reject Him, and He has sworn that anything which He has included in Scripture is meant to do us good, whether we like it or not (2 Timothy 3:12-17). So we know that all these warnings are directed toward Christians to keep us safe in the same way that we warn our own children not to touch hot stoves or play in the middle of the road. I won't dwell on this point though in this post. My main purpose in writing right now is to encourage God's frightened sheep, and the only reason I am emphasizing the reality behind those warning passages in Scripture right now is because I do not think any real comfort can be had from God's word by treating it as a buffet from which we take what we like. It is a meal which must - as much as we have the means - be taken as a whole or the result will almost certainly be worse than if we had ignored it entirely. So in order to offer you any worthwhile comfort, I am compelled to first make sure we are on the same page that the Lord never wastes a word (Isaiah 55:10-12).
That's the hard part out of the way. If you're still with me, I'd like to turn your attention to a few encouragements from Scripture regarding the Lord's great mercy. The first and probably the most visceral is this. The Bible records accounts of many people who have committed great and terrible sins and have been saved. Abraham not only lied by telling people his wife was his sister for fear that he would be killed by men who would want to take her for their own wife but he also caused her to lie in the same way (Genesis 12:10-20, Genesis 20:1-14). The lie even went so far that if the Lord had not intervened, it would have had catastrophic consequences for at least one nation. David had Uriah, a soldier of extraordinary faithfulness murdered so that he could cover up his adultery with Uriah's wife (2 Samuel 11:1-12:23). And the apostle Thomas refused to believe even the testimony of the other apostles that Christ had risen from the dead, saying "unless I see in His hands the imprint of the nails, and put my finger into the place of the nails, and put my hand into His side, I will not believe" (John 20:19-29). But we have God's own account of these men as faithful to and beloved by Him.
I would also call your attention to the fact that in all of Scripture there are very few things which we are told make salvation impossible for a person. Under the Law in the Old Testament, high handed sins - that is, sins committed in blatant defiance of the Lord and His Law - bore a death sentence, and no provision was made for their forgiveness, but since David very clearly knew how evil adultery and murder were and did them anyway, we can only conclude that either the Lord kept and exercised the right to overrule the Law even then and show mercy or, less likely I think, that even such sins as David's in that matter did not cross the threshold of high handedness. The New Testament warnings about blasphemy against the Holy Spirit and apostasy are even more severe than the law against high handed sins in the Old Testament, but they are also extremely specific. Christ's own words indicate unambiguously that the only sin which is truly unforgivable is blasphemy against the Holy spirit. He even doubles down, saying that even blasphemy against Himself will be forgiven, only not against the Holy Spirit. Since Scripture does not contradict itself, it seems the only possibility then is that the apostasy Hebrews warns against is not an additional unforgivable sin Christ failed to mention but a form of the same sin. If that is true then even what is called backsliding, which for many people is the source of the fear I am addressing here, is not what Hebrews is warning against. The kind of apostasy in view there seems to necessarily involve a complete repudiation of the Holy Spirit.
And one more encouragement. Not one example given in Scripture of those who were beyond salvation ever showed the slightest interest in being saved from their sins. Esau wept over his lost blessing but not over having sold it. Judas hanged himself but did not seek forgiveness. The scribes and Pharisees and Sadducees who conspired to have Christ murdered - and who prompted His warning about blasphemy against the Holy Spirit - went far beyond merely not showing any interest in salvation. They actively worked to draw others into their web and to pull down upon themselves, their dupes, and the descendants of all involved the Lord's retribution for the shedding of Christ's blood. All of these might have liked to be saved from Hell if only they could keep their sins, but they were determined to keep their sins at any price. On the other hand, everyone in the Bible who expressed any desire to be reconciled with God received mercy. David, though he was disciplined for it, was forgiven for his murder of Uriah and adultery with Bathsheba. Peter was forgiven for openly denying Christ three times in one night (Luke 22:54-62, John 21:15-17). Paul was forgiven for actively working to have Christians imprisoned and put to death. We can be sure, given these examples on both sides of the issue, that no one who truly wants to have Christ as their King will fail to have Him as their savior as well.