Is the sin of unbelief the only sin that will cause one to not inherit eternal life and to be thrown into the lake of fire? The Biblical answer is a categorical, No. In contrast to Biblical truth, the message of once saved always saved declares the sin of unbelief to be the only sin which will send one to hell, to the shame of all who teach it and those who believe it!
Remember, the eternal security teachers deny that murder, sexual immorality, theft, swindling, slander, lying, drunkenness or any other sin (in any combination) can send a person once saved to the lake of fire. The ramification of that heresy is, the only sin that will cause one to be thrown into the fiery furnace is a constant state of unbelief before receiving eternal salvation!
The famed Charles Spurgeon was not the Prince Of Preachers, as many wrongly call him, for his doctrines had Biblical errors, as a Calvinist. As a Calvinist he believed, when king David sinned with adultery and murder, he retained his salvation, as did John Calvin. It goes with that false theology and license to sin. But that is not all Spurgeon believed. Here is what the same grace changer, Charles Spurgeon, said about the sin of unbelief:
… if you are damned, it will be unbelief that damns you. (Charles Spurgeon, The Sin of Unbelief, January 14, 1855)
If Spurgeon and multitudes of others are wrong, what Scripture/s can prove it? God, from his own throne in heaven, powerfully refuted that fallacious concept with this:
But the cowardly, the unbelieving, the vile, the murderers, the sexually immoral, those who practice magic arts, the idolaters and all liars–their place will be in the fiery lake of burning sulfur. This is the second death. (Rev 21:8)
According to God himself, along with a host of others, the unbelieving will find his home in the lake of fire. The unbelieving will be with the cowardly, the vile, the murderers, the sexually immoral, those who practice magic arts, the idolaters and all liars. That is not even a complete listing, but the point has been made already. It seems the chief stumbling block for the concept of only the sin of unbelief comes from John 3:18. That verse says:
He who is believing in him is not judged, but he who is not believing hath been judged already, because he hath not believed in the name of the only begotten Son of God. (Young’s Literal)
That verse focuses in upon the present time, and only mentions two types of people: either the ones believing in Jesus or the ones not believing. That, however, is not an all-inclusive listing of people who will get eternal life or be eternally lost, as we already saw from Rev. 21:8. Besides John 3:18, Jesus also gave us Luke 8:12-15 which refers to the various types of people who heard the word of God and what their reactions were. Verse 12 refers to those who were never saved (and always in the sin of unbelief). Verse 13 are those who were once saved, but afterwards became unbelieving through persecution. Verse 14 are those who don’t bring forth fruit because of the cares of this life, etc. and are apparently thrown into the fire too (John 15:1-6). So again, as in Rev. 21:8, the sin of unbelief is separated from other lethal forms of behavior. The people who teach the sin of unbelief is the only sin which will send one to the lake of fire are making excuses for all other sins, downplaying them. Don’t be deceived. Ponder 1 Cor. 6:9,10; Eph. 5:5-7, Gal. 5:19-21, Rev. 22:15; etc. Sin is still the issue.