There are five unforgivable sins for man, but only four can cause the lose of salvation, contrary to popular belief, suicide in NOT one of them.
When Jesus spoke of the unforgivable sin it was with respect to “blasphemy against the Holy Spirit” which is mentioned in Mark 3:22–30 and Matthew 12:22–32.
“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. And whosoever speaketh a word against the Son of man, it shall be forgiven him: but whosoever speaketh against the Holy Ghost, it shall not be forgiven him, neither in this world, neither in the world to come.” Matthew 12: 31–32
The term blasphemy may be generally defined as “defiant irreverence.” The term can be applied to such sins as cursing God or willfully degrading things relating to God. Blasphemy is also attributing some evil to God or denying Him some good that we should attribute to Him. This particular case of blasphemy, however, is called “the blasphemy against the Holy Spirit” in Matthew 12:31. The Pharisees, having witnessed irrefutable proof that Jesus was working miracles in the power of the Holy Spirit, claimed instead that the Lord was possessed by a demon (Matthew 12:24). Notice in Mark 3:30 Jesus is very specific about what the Pharisees did to commit blasphemy against the Holy Spirit: “He said this because they were saying, ‘He has an impure spirit.’”
Blasphemy against the Holy Spirit has to do with accusing Jesus the Christ of being demon-possessed instead of Spirit-filled. This particular type of blasphemy cannot be duplicated today. The Pharisees were in a unique moment in history: they had the Law and the Prophets, they had the Holy Spirit stirring their hearts, they had the Son of God Himself standing right in front of them, and they saw with their own eyes the miracles He did. Never before in the history of the world (and never since) had so much divine light been granted to men; if anyone should have recognized Jesus for who He was, it was the Pharisees. Yet they chose defiance. They purposely attributed the work of the Holy Spirit to the devil, even though they knew the truth and had the proof. Jesus declared their willful blindness to be unpardonable. Their blasphemy against the Holy Spirit was their final rejection of God’s grace. They had set their course, and God was going to let them sail into perdition unhindered.
Jesus told the crowd that the Pharisees’ blasphemy against the Holy Spirit “will not be forgiven, either in this age or in the age to come” (Matthew 12:32). This is another way of saying that their sin would never be forgiven, ever. Not now, not in eternity. As Mark 3:29 puts it, “They are guilty of an eternal sin.”
The immediate result of the Pharisees’ public rejection of Christ (and God’s rejection of them) is seen in the next chapter. Jesus, for the first time, “told them many things in parables” (Matthew 13:3; cf. Mark 4:2). The disciples were puzzled at Jesus’ change of teaching method, and Jesus explained His use of parables: “He answered and said unto them, Because it is given unto you to know the mysteries of the kingdom of heaven, but to them it is not given.. . . . Therefore speak I to them in parables: because they seeing see not; and hearing they hear not, neither do they understand.” Matthew 13:11, 13
Jesus began to veil the truth with parables and metaphors as a direct result of the Jewish leaders’ official denunciation of Him. Again, the blasphemy of the Holy Spirit in the context of attributed the works of the Holy Spirit through Jesus the Christ cannot be repeated today, although the other aspects of blasphemy still apply. Jesus Christ is not on earth—He is seated at the right hand of God. No one can personally witness Jesus performing a miracle and then attribute that power to Satan instead of the Holy Spirit.
The unpardonable sin today is the state of continued unbelief. The Spirit currently convicts the unsaved world of sin, righteousness, and judgment (John 16:8). To resist that conviction and willfully remain unrepentant is to “blaspheme” the Spirit. There is no pardon, either in this age or in the age to come, for a person who rejects the Spirit’s promptings to trust in Jesus the Christ and then dies in unbelief.
“For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.” John 3:16
“He that believeth on the Son hath everlasting life: and he that believeth not the Son shall not see life; but the wrath of God abideth on him.” John 3:36
The extent of what is unforgivable to God, from a Biblical basis is as follows:
Blasphemy of the Holy Spirit (Matthew 12:31-32; Luke 12:10)
Accepting the mark of the Beast – (Revelation 14:9-10) (Salvation lost) This can only take place during he tribulation.
Worshipping the image of the Beast (Rev 14:9-10) – (Salvation lost) Also only during the tribulation.
Taking away from the Book of Revelation (Rev 22:19) – (Salvation lost and the only sin that can be done in this lifetime)
Joining Satan’s Army after he is loosed from prison after the thousand year reign (Revelation 20:7-10) – (Salvation lost)