Each book also addresses deceivers and teachers who no longer acknowledge that Jesus is the Messiah or Son of God. They are instead spreading fear and division among Jesus’ followers. 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 also reminds believers to welcome true missionaries who teach the message of the cross and love others. They should not welcome deceivers or make idols of anything that exalts itself in God's place.