Take a look at these two puzzling passages from the New Testament.

Mark 3:28-29:

²⁸ Truly I tell you, people can be forgiven all their sins and every slander they utter,

²⁹ but whoever blasphemes against the Holy Spirit will never be forgiven; they are guilty of an eternal sin.”

Matthew 12:30-32:

³⁰ “Whoever is not with me is against me, and whoever does not gather with me scatters.

³¹ And so I tell you, every kind of sin and slander can be forgiven, but blasphemy against the Spirit will not be forgiven.

³² Anyone who speaks a word against the Son of Man will be forgiven, but anyone who speaks against the Holy Spirit will not be forgiven, either in this age or in the age to come.

What can it mean?

Well, here’s a post by Dr. Paul Gould to shed some light on it.

Excerpt:

Taken in isolation, it is hard to make sense of this passage—how is it that all kinds of sins can be forgiven but one sin will not be forgiven? What is going on here? Well, here is a principle of sound biblical interpretation:

Principle #1: In order to correctly understand a passage, we must always look at it within its context.

And what is the passages context? The broader context can be found in Matthew 12:22-32. In this broader context we read of Jesus performing a miracle (he performs an exorcism and heals a blind and mute man), we read of the crowd’s amazement and wonderment over the identity of Jesus (“Could this be the Son of David?”), we find the slanderous (and murderous) charge of the Pharisees, and we find Jesus’ response to the Pharisees charge (both his reasoned response to their explicit charge that he drives out demons by Satan’s power as well as his warning to the Pharisees if they continue to attribute to Satan what is in fact the work of God’s Spirit).

After looking at this passage in context, we find that the “unforgivable sin” is (basically) attributing what is in fact the work of God’s Spirit to His ultimate enemy, Satan.

Fair enough, you say, but there are other problems passages that talk about the unforgivable sin—Hebrews 6, 1 John 5, and Hebrews 10 come to mind. What about those passages? Well, here is our second principle of biblical interpretation:

Principle #2: Always interpret unclear passages in light of the clear teachings of Scripture (as a whole).

And what is the clear teaching of Scripture related to sin and forgiveness? It is this:

Forgiveness of sins is a consequence of man’s repentance, and repentance is a consequence of the activity of the Holy Spirit in our hearts. So in the end, it seems that blasphemy against the Holy Spirit is nothing more or less than the unrelenting rejection of His advances.

So, the only unforgiveable sin is the sin of deliberately rejecting God’s efforts to draw you into a saving relationship with him. What does this mean for you? It means that if you are a Christian and you believe the essentials of the faith, then you aren’t going to be able to lose your salvation by performing sinful actions. You can’t sin your way out of God’s forgiveness, because if you accept Jesus’ death as payment for your sins, then it covers all your sins. I do think that the Bible is very clear that you can lose your salvation by “the unrelenting rejection” of God’s advances. But that’s not a description of any Christians, it’s a description of someone who does not believe in Jesus.