Matthew 12:24-32 "Whoever speaks a word against the Son of Man will be forgiven, but whoever speaks against the Holy Spirit will not be forgiven, either in this age or in the age to come" ( v. 32).
Of all the teachings of Jesus, perhaps none troubles us more than His warning about blaspheming the Holy Spirit. When reading today's passage it is only natural to ask, "What is the unforgivable sin?" and, "Have I committed it?"
Many in church history have identified the unforgivable sin as divorce, adultery, or another grievous sin, or they have said God will not forgive those who do even one evil deed after baptism. That so many options have been suggested illustrates the complexity of Matthew 12:24-32. We must, therefore, humbly approach the topic of the unforgivable sin, aware that we cannot be too cautious when applying today's verses. Let us also note that even heinous sins are forgivable. Christ pardoned Peter for denying Him (John 18:15-27; 21:15-19). David repented and was forgiven for murder and adultery ( 2 Sam. 11:1-12:15a). Paul was made an apostle even though He once persecuted Jesus (Acts 9:1-19).
The meaning of Matthew 12:32 is clearer when we consider the passage in its totality (vv. 22-32 ). Even though they should know better, the Pharisees attribute Jesus' exorcisms to the power of the Devil (v. 24). This is absurd since it is irrational for Satan to cast out his own minions and tear down his own kingdom (vv. 25-26). Moreover, if Jesus exorcises demons by the Devil's power, then the followers of the Pharisees who do the same must also be acting under the Adversary's influence, a deduction these scholars cannot endorse ( v. 27). These teachers inconsistently accuse Jesus of being in Satan's thrall while seeing God at work among their own students. Stubbornly and persistently, the Pharisees are attributing the work of the Holy Spirit in Christ's ministry to the Devil.
Dr. R.C. Sproul says the unforgivable sin is blaspheming against the Holy Spirit by calling Jesus a devil after being enlightened by that same Spirit. According to John Calvin, we commit such sacrilege "only when we knowingly endeavor to extinguish the Spirit." There can be no salvation if the work of the Spirit is knowingly rejected. This act reveals a heart so hard that repentance is impossible (Heb. 3:7-19). Ultimately, as Augustine says, "It is unrepentance that is a blasphemy against the Spirit" (Nicene and Post-Nicene Fathers, Vol. 1, 6:325).