How can you know if you, or a friend, or relative, have committed the unforgivable sin?
Believers Cannot Commit the Unforgivable Sin
First, if you have believed in Jesus Christ for eternal life, then it is no longer possible for you to blaspheme the Holy Spirit.
Since you have believed in Jesus for eternal life, the Holy Spirit has ceased the work upon you which He performs on unbelievers, and is now living within you to mold and shape you into Christlikeness. Due to this, a Christian can quench and grieve the Holy Spirit, but cannot blaspheme the Spirit in the way Jesus talks about in Matthew 12:31-32.
If you are a believer, do not worry about committing the unpardonable sin. The possibility of committing the unforgivable sin is forever in your past.
Unbelievers who Worry about the Unforgivable Sin Have Not Committed It
If, however, you are not a Christian, and worry that you might have committed the unforgivable sin, be encouraged. Nobody who commits the blasphemy against the Spirit wonders if they have.
They no longer care about such things.
The unbeliever who commits the unforgivable sin has become so morally and spiritually blind that their heart is hardened. They Holy Spirit has stopped trying to convince them of sin, righteousness, and judgment. As a result, they have become fully enslaved to sin, to the point that they no longer care about spiritual things and will never believe in Jesus.
Such a condition is clearly not true of you, because you are reading this book and are concerned about your spiritual state. This proves that the Holy Spirit is still working on you, and therefore, you have not yet committed the unforgivable sin.
A Warning about the Unforgivable Sin
But be warned.
If you have not yet believed in Jesus for eternal life, then the warning that Jesus gave to the religious leaders in Matthew 12:31-32 may apply to you as well.
Jesus told the Pharisees that if they continued to reject the truths which were clearly before their eyes, then there may come a day when the Spirit stops trying to convince them.
So if you have not believed in Jesus for eternal life, do not resist the Spirit any longer. There is still time. Do not delay. Receive eternal life and become a member of God’s family by believing in Jesus Christ (John 3:16; 5:24; 6:47).
Once you have believed in Jesus for eternal life, the possibility of committing the unforgivable sin becomes an impossibility forever.