Here is the unforgivable sin that is mentioned in the Bible:
“I tell you the truth, people will be forgiven for all sins, even all the blasphemies they utter. But whoever blasphemes against the Holy Spirit will never be forgiven, but is guilty of an eternal sin” (because they said, ‘He has an unclean spirit’).” (Mark 3:28–30)
But there is another one that is rarely talked about that is unforgivable, an unforgivable sin that can only be committed during the Antichrist’s great tribulation:
“A third angel followed the first two, declaring in a loud voice: “If anyone worships the beast and his image, and takes the mark on his forehead or his hand, that person will also drink of the wine of God’s anger that has been mixed undiluted in the cup of his wrath, and he will be tortured with fire and sulfur in front of the holy angels and in front of the Lamb. And the smoke from their torture will go up forever and ever, and those who worship the beast and his image will have no rest day or night, along with anyone who receives the mark of his name.” This requires the steadfast endurance of the saints—those who obey God’s commandments and hold to their faith in Jesus.” (Rev 14:9–12)
There have been those who have tried to argue that if someone (believer or unbeliever) commits this sin, they will be able to repent of it later.
The problem with this is three-fold:
1. The passage does not hint at such a prospect at all. Rather, the language goes out of its way to warn anyone of its consequences for doing such a thing, piling up graphic descriptions of wrath. It is the most descriptive passage of hell in the Bible, for a reason. It signals to the reader that you will seal your fate if you do this. Interestingly, this is the same category of sin that the traditional unforgivable sin in Mark 3:28–30 falls into: blasphemy of the Holy Spirit. But in this case the blasphemy against the Holy Spirit (God) is worshiping the beast and its image through taking the beast’s mark.
2. The book of Revelation as a whole conveys that the beast-followers who have taken the mark will not repent (See Rev. 9:20–21; 16:9, 11). This is a judgment by God in itself, by taking the mark God judges them with a hardened heart. I think 2 Thessalonians 2:9–12 is relevant to this context: “The arrival of the lawless one will be by Satan’s working with all kinds of miracles and signs and false wonders, and with every kind of evil deception directed against those who are perishing, because they found no place in their hearts for the truth so as to be saved. Consequently God sends on them a deluding influence so that they will believe what is false. And so all of them who have not believed the truth but have delighted in evil will be condemned.”
3. People are always trying to twist and strain Scripture by trying to explain some supposed loophole for those who take the mark and can repent later. If this happens in your lifetime, don’t rationalize to yourself saying things like, “God will understand if I take the mark, because I need to feed my children.” Or, “I will just take the mark but not worship the beast and his image.” Seriously? You want to risk your soul playing games with Scripture twisting or rationalizing God’s Word? I can tell you right now that God is not in the loophole business. In this passage, and the book of Revelation as whole, clearly teach that taking the mark is a sign that you have given your allegiance to Antichrist. There are no exceptions to taking the mark. This is not a game. Your soul depends on your decision to either follow Antichrist, or Christ.
How can you be sure to avoid this other unforgivable sin mentioned in the Bible? Do not take the mark. “This requires the steadfast endurance of the saints—those who obey God’s commandments and hold to their faith in Jesus” (Rev 14:12).