In Christian hamartiology, eternal sin, the unforgivable sin, unpardonable sin, or ultimate sin is the sin which will not be forgiven by God. One eternal or unforgivable sin (blasphemy against the Holy Spirit), also known as the sin unto death, is specified in several passages of the Synoptic Gospels, including Mark 3:28–29, Matthew 12:31–32, and Luke 12:10, as well as other New Testament passages including Hebrews 6:4–6, Hebrews 10:26–31, and 1 John 5:16.
The unforgivable sin is interpreted by Christian theologians in various ways, although they generally agree that one who has committed the sin is no longer able to repent, and so one who is fearful that one has committed it has not done so.
New Testament passages
Several passages in the New Testament are frequently interpreted as referring to the unforgivable sin: Matthew 12:30-32: "Whoever is not with me is against me, and whoever does not gather with me scatters. Therefore I tell you, people will be forgiven for every sin and blasphemy, but blasphemy against the Spirit will not be forgiven. 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." Mark 3:28–30: "Truly I tell you, people will be forgiven for their sins and whatever blasphemies they utter; but whoever blasphemes against the Holy Spirit can never have forgiveness, but is guilty of an eternal sin—for they had said, "He has an unclean spirit."" Luke 12:8–10: "And I tell you, everyone who acknowledges me before others, the Son of Man also will acknowledge before the angels of God; but whoever denies me before others will be denied before the angels of God. And everyone who speaks a word against the Son of Man will be forgiven; but whoever blasphemes against the Holy Spirit will not be forgiven." Hebrews 6:4–6: "For it is impossible to restore again to repentance those who have once been enlightened, and have tasted the heavenly gift, and have shared in the Holy Spirit, and have tasted the goodness of the word of God and the powers of the age to come, and then have fallen away, since on their own they are crucifying again the Son of God and are holding him up to contempt." Hebrews 10:26–31: "For if we willfully persist in sin after having received the knowledge of the truth, there no longer remains a sacrifice for sins, but a fearful prospect of judgment, and a fury of fire that will consume the adversaries. Anyone who has violated the law of Moses dies without mercy "on the testimony of two or three witnesses." How much worse punishment do you think will be deserved by those who have spurned the Son of God, profaned the blood of the covenant by which they were sanctified, and outraged the Spirit of grace? For we know the one who said, "Vengeance is mine, I will repay." And again, "The Lord will judge his people." It is a fearful thing to fall into the hands of the living God." 1 John 5:16: "If any man see his brother sin a sin which is not unto death, he shall ask, and he shall give him life for them that sin not unto death. There is a sin unto death: I do not say that he shall pray for it."
Teaching by Christian denomination
Eastern Christianity
The importance of prayer (1 Thessalonians 5:17: "pray without ceasing") and humility (Jesus Prayer: "Lord Jesus Christ, Son of God, have mercy on me, a sinner") in Christianity is reflected by an Orthodox catechism as follows:
Roman Catholicism
The Church Fathers considered additional interpretations other than it being to attribute the Holy Spirit's works to Satan with Augustine of Hippo calling it one of the more difficult passages of Scripture. Thomas Aquinas summarized the Church Fathers' treatments and proposed three possible explanations: That an insult directed against any of the Three Divine Persons may be considered a sin against the Holy Spirit; and/or; That persisting in mortal sin till death, with final impenitence, as Augustine proposed, frustrates the work of the Holy Spirit, to whom is appropriated the remission of sins; and/or; That sins against the quality of the Third Divine Person, being charity and goodness, are conducted in malice, in that they resist the inspirations of the Holy Spirit to turn away from or be delivered from evil. Such sin may be considered graver than those committed against the Father through frailty, and those committed against the Son through ignorance.