What does 1 John 2:26 mean?

Verses 12–14 mention "writing" or "I write" six times. Verse 21 adds another. This verse adds an eighth. Each occasion introduces something John desires to emphasize. In this case, he draws attention to the false teachers he calls antichrists in verses 18–27. These false teachers denied Jesus was the Christ (1 John 2:22). They did not have both the Father and the Son.

According to John, these people are attempting to deceive the believers. People can be deceived by themselves (1 John 1:8), by others (1 John 3:7), and, as mentioned here, by false teachers. Second John 1:7 adds, "For many deceivers have gone out into the world, those who do not confess the coming of Jesus Christ in the flesh. Such a one is the deceiver and the antichrist." In Revelation 12:9, one of the five names of Satan is "the deceiver of the whole world." Satan is the ultimate source of deception, which explains why John referred to false teachers as antichrists.