Read Mark 3:28-29
28 “Listen to this carefully. I’m warning you. There’s nothing done or said that can’t be forgiven. But if you persist in your slanders against God’s Holy Spirit, you are repudiating the very One who forgives, sawing off the branch on which you’re sitting, severing by your own perversity all connection with the One who forgives.” He gave this warning because they were accusing him of being in league with Evil. (THE MESSAGE)
From time to time, people start worrying about whether they have committed the unforgivable sin. Ironically, the very fact that they are worried is an indication they have not committed such a sin.
The so-called unforgivable sin is not some particularly wicked act we might do. Think of the very worst thing a human being might do to another human: that sin can be forgiven if the offenders fling themselves on the mercy of Jesus. Jesus didn’t die on the cross to cover just about all sins with a few exclusions mentioned in the fine print. He died to cover all sins.
So why is there such a thing as the unforgivable sin? As our paraphrase text indicates, it is to do with ongoing rejection of the mercy offered by Jesus. To deny Jesus is the Saviour, which is what his opponents were doing, is to rule oneself out of mercy. The unforgivable sin is to deny the witness the Spirit bears to Jesus as being the source of our salvation. Or to put it more simply, it is to deny the one and only possibility of forgiveness. So, logically, such a sin is unforgivable.
And we need to note that such a denial has to be ongoing till our dying breath. Many reject Jesus at one point and yet come to accept him at a later point. So we can never conclusively say we or anyone else has committed this sin. Forgiveness remains on offer to all who both know their need of it and recognise the source of it.