No one in their right mind should want to commit the “Unpardonable Sin.” Jesus identified that sin in Matthew 12 when the Pharisees, the leaders of Israel, accused Him of casting out devils by the power of Beelzebub, the prince of devils. (Matt. 12:24) Jesus reasoned in response to their unbelief that Satan would be divided against himself if “Satan cast out Satan.” In this context, Jesus declared that attributing to Satan the works of the Holy Ghost was the sin for which there would be no forgiveness “neither in this world nor in the world to come.” (Matt. 12:32) When the Pharisees, acting on behalf of the nation, officially rejected Jesus as Messiah, that was, for Israel, crossing the point of no return, nationally, and it was for the nation at that time the “Unpardonable Sin.”
In Matthew 13, therefore, in order to graciously shield the unbelieving nation from more severe judgment in the day when all whose names are not written in the Book of Life will be cast into the lake of fire (Rev. 20:15), Jesus began to employ parables because “seeing they see not; and hearing they hear not, neither do they understand.” (Matt. 13:13) This statement answered the disciples’ question, “Why speakest thou in parables?” (v.10) Jesus had already taught them that it would be more tolerable for cities such as Sodom and Gomorrah, Tyre and Sidon, than it would be for the cities to which He had come preaching the gospel of the kingdom only to be rejected. (Matt. 10:15; 11:20-24) These cities, Chorazin, Bethsaida and others in Jesus’ day had received and rejected more light, therefore, in the judgment day (Rev.20:11-15) there would be more severe punishment meted out; so, in the light of that, Jesus graciously withheld more light from the people that had officially said “No!” to His offer of the kingdom. They, as a nation, had already committed the “Unpardonable Sin.”
The sin unto death is a different matter, and it is mentioned specifically by the Apostle John in his first epistle, chapter five. It is sin that can be committed by believers, and the “death” that is mentioned by John is not the second death, or eternal damnation, but a physical, pre-mature death divinely meted out to wayward believers who, having lapsed into sin and having been admonished and rebuked spiritually (Gal.6:1,2; Matt. 18:15-20) continue to go on sinning so that God administers the ultimate chastening upon them, physical death, so as not to allow them to cause others to stumble over their harmful testimony. Paul, in his first letter to the church in Corinth, says that many had ignored God’s convicting Spirit and were still partaking of the Lord’s Table with known, unconfessed sin in their lives, drinking damnation (judgment) to “himself, not discerning the Lord’s body.” (I Cor. 11:29) Paul concluded that “for this cause many are weak and sickly among you, and many sleep.” (I Cor. 11:30) The sleep here mentioned is the sleep of (physical) death, and it was a warning to believers that each should “examine himself and so let him eat of that bread, and drink of that cup.” (I Cor. 11:29)
It should be noted that in the passage in I John where John speaks of a brother who is observed sinning “a sin which is not unto death,” (v.16) the definite article does not appear in the Greek text so that the brother is not sinning one certain sin, he is, however, sinning sin which has not yet resulted in sinning unto death. This brother should be, as the Spirit of God leads, the object of our prayers. In fact, James in his epistle, tells us that if a brother errs from the truth and one of us gets him turned around (converted, but not in the sense of soul salvation), then “he which converteth the sinner from the error of his way shall save a soul from death….” (James 5:19,20) We can, then, as concerned, loving brothers in Christ, be used of God to rescue an erring brother or sister in Christ from sinning sin that eventuates in death, sin unto death.
So, the Unpardonable Sin was committed in about 29 or 30 A.D. by the nation of Israel. People can reject God’s simple plan of salvation and be cast into the lake of fire from whence there is no return and for which there is no “2nd chance,” and in that sense a lost person can commit a sin for which there will never be forgiveness in eternity; but that, technically and scripturally speaking, is not the Unpardonable Sin: it was committed by the nation of Israel in its rejection of their Messiah. Sin unto death can be and is being committed by brethren who have been overcome by sin and who refuse to repent and be restored to fellowship with their Lord and with His church. It is a grave sin for which there are serious consequences; but it is not a sin that will send a person to hell.
“Wherefore I say unto you, All manner of sin and blasphemy shall be forgiven unto men: but the blasphemy against the Holy Ghost shall not be forgiven unto men.” (Matt.12:31)