John 1-3 addresses a changing tide in the early church, deceivers and teachers who no longer acknowledge that Jesus is the Messiah or the Son of God. They are spreading fear and division among believers. John says that all legitimate teachers will share the truth about Jesus and the cross, love others sacrificially, and spread love and light rather than fear.

He reminds believers to welcome true missionaries who teach the Gospel and love others. They should not welcome deceivers or make idols of anything that exalts itself in God's place.