The New Testament authors speak of many kinds of people, two of which, include false teachers and false brothers. I mention this, because I think it is important to draw a distinction between the two. A false brother is someone who is idle (2 Thes. 3:6) and/or living in continual sin (Gal 5:21). These are people we are not to associate with, yet, there seems to be hope for these false brothers. As Paul states in 2 Thes. 3:15, “Do not regard him as an enemy, but warn him as a brother.” So there are people who claim the name of Christ but walk according to the flesh, but there are also prophets and teachers who claim the name of Christ and likewise walk according to the flesh teaching another gospel.
In a general sense a false teacher is anyone who teaches against Christ, which would include teachers of pagan religions. Yet, when the scripture speaks of false teachers it does not seem to have those sorts of people in mind, but rather those who identify themselves as Christ’s. They are spoken of as wolves in sheep’s clothing (Matt. 7:15), compared to Satan who is disguised as an angel of light (2 Cor. 11:14), having an appearance of godliness (2 Tim 3:5), bringing in secret heresies (2Pet. 2:1), spies on our freedom (Gal. 2:4), and creeping in unnoticed (Jude 1:4). Jesus warned us, “See that no one leads you astray. For many will come in my name, saying, ‘I am the Christ,’ and they will lead many astray,” (Matt. 24:4-5). John wrote, “They went out from us, but they were not of us,” (1John 2:19). Paul reminds us, “Now the Spirit expressly says that in later times some will depart from the faith by devoting themselves to deceitful spirits and teachings of demons…” (1 Tim. 4:1). All of these descriptions make it clear that these people were associated with the name of Christ in some sense. These are a special group of people different from pagan worshippers and teachers because these persons have lead people astray to believe false gospel.
The preceding distinction is necessary in order to understand why Paul and the others reacted so strongly, and for our sake’s, so we might know what to pray for. It is true that all who do not already believe are condemned (John 3:18) and that they are likewise children of wrath as we once were (Eph. 2:3), but there is a special condemnation and a stricter judgment for false teachers (James 3:1). Peter tells us, “And in their greed they will exploit you with false words. Their condemnation from long ago is not idle, and their destruction is not asleep,” (2 Pet. 2:3). Likewise, Jude states, “For certain people have crept in unnoticed who long ago were designated for this condemnation, ungodly people, who pervert the grace of our God into sensuality and deny our only Master and Lord, Jesus Christ,” (Jude 1:4). Paul wrote, “Just as Jannes and Jambres opposed Moses, so these men also oppose the truth, men corrupted in mind and disqualified regarding the faith,” (2 Tim 3:8). In another place he said, “Their end is destruction…” (Phil 3:19). Peter calls them “accursed children!” (2 Pet. 2:14). Paul says, “Let [them] be accursed,” (Gal 1:9) and wishes they would emasculate themselves (Gal 5:12). All of this leads me to conclude that there is no hope of salvation for those who "boldly and willfully” blaspheme the glorious ones (2 Pet 2:10; Jude 1:8). Their end, instead, is destruction and our attitude towards them is not to be one of acceptance and tolerance, but rather speaking out against them so people will not be led astray (Eph 5:11). If you find all of these things challenging to believe, know you are not alone. Although Paul called out false teachers as with Alexander the coppersmith (2 Tim 4:14-15), he also cried with tears because of those walking as enemies of the cross (Phil. 3:18-19). Surely, he cried in part because people were being led astray, but I think also he was sorrowful because the enemies were headed to hell (See Rom. 9:1-3).
While none of this is easy, I think it is encouraging to know how to respond to and feel about false teachers. It’s helpful to know where our focus ought to be and comforting knowing that these false teachers are the ones causing divisions (Jude 1:19;Rom16:17), not those standing firm in the truth. Be encouraged if you are contending for the faith, for this is what we are called to do. Consider Eph. 5:11, “And have no fellowship with the unfruitful works of darkness, but rather reprove them.”
Like Peter I pray that, "You therefore, beloved, knowing this beforehand, take care that you are not carried away with the error of lawless people and lose your own stability.But grow in the grace and knowledge of our Lord and Savior Jesus Christ. To him be the glory both now and to the day of eternity. Amen," (2 Pet. 3:17-18).