In 1 John 2:18-27, John warns believers about the emergence of the antichrist, those who deny Jesus as the Christ, emphasizing the urgency of the last hour. He cautions against deceivers and urges the faithful to remain steadfast in the truth they have received. This passage highlights the importance of vigilance, encouraging believers to hold firm to their faith in Jesus and rely on the anointing of the Holy Spirit to discern and resist false teachings.