How do you recognize brothers and sisters in the faith from those who are not? What about the groups we call cults? How do you recognize the dangers that they entail? This shortest book in the Bible addresses these important questions.

Different Christian denominations do some things differently than we do. Yet we can recognize them as brothers and sisters in Christ. The command we have from Christ is not a new one, but an old one…that we love one another (v 5). They may understand things differently from the way we do. Some of these differences are slight. Some are more important, but on the all-important issue, Christian groups agree. That issue is Christ himself. Here is how you can recognize whether a group is Christian or not. What do they teach, preach, worship, believe and live about Christ? The central item of Christianity is Christ.

There are groups that use Christian in their name (Christian Science, Mormon) that do not have a vital understanding of Christ. Islam has some very complimentary things to say about Jesus, but it does not have an acceptable understanding of Christ. Jehovah’s Witnesses and Unitarians have sprung up on "Christian soil" but they are not Christian.

Many deceivers, who do not acknowledge Jesus Christ as coming in the flesh have gone out into the world. Any such person is the deceiver and the antichrist (v 7). Those teachers who do not acknowledge Christ come in the flesh are antichrist and may lead you astray. Avoid them.

Before considering the heresy that worried the Apostle John, consider right thinking (orthodoxy) concerning the Lord Jesus. The Church recognized that Jesus was a human being. He was born and lived like us. In fact, aside from sin, he knew and experienced every part of the human condition. Christ had to be a human being to atone for human sin. The Church also recognized Jesus as the Son of God, as the manifestation of God himself. They worshiped him as the risen Lord, as the Lamb upon the throne of heaven. Thomas looked at the resurrected Christ and exclaimed, "My Lord and my God."

From the Scriptures and the person of Christ, the Church has always known these two natures of Christ—both human and divine. At the Church council of Chalcedon in AD 451, the Church formulated a statement concerning Christ that all Christians have affirmed. Our own Shorter Catechism describes the Redeemer of God’s elect as God and man in two distinct natures, and one person forever (A 21). Both natures are needed for Christ to be the Redeemer.

What was the problem that the apostle wrote about in this letter? There were deceivers who said that Christ had not come in the flesh. These teachers might say that Christ was God or at least a heavenly being, but they denied that he was human. There were a lot of teachers out there who said, "The body is evil. Things you can touch are evil. God is a Spirit and only cares about spirit. Jesus could not have really been human."

These teachers are wrong. God created our body and said, "It is good." God cares about our bodies which is why we pray for physical healing. God answers prayer because he loves us. Christ came to share our life as human beings because God loves us. The Apostle says don’t listen to those teachers who miss this big point about Christ. Don’t listen to those who say they have a teaching that goes beyond Christ. Listen to those who stay focused on the Lord Jesus Christ, who at the cost of his own blood fully paid for all of our sins.

Whoever continues in the teaching has both the Father and the Son (v 9). The gospel tells us about Jesus Christ and God’s love for us shown in him. If you want to know the blessing of God the Father, you need to know the Son as well. Don’t be fooled by someone who wants to teach a new or better way to know God the Father. Verse 10 tells us not to support them or even welcome such teachers into our midst. If they lead you away from Jesus Christ, they lead you astray.

You have people all the time who want to teach you things about God. They may knock on your door. They may broadcast over the radio or TV. How do you know if you can trust what they are saying? It is important for you to take this seriously.

The purpose of this letter is not just to guard believers from false teachers. The goal is that you know the truth so you are walking in the truth. It has given me great joy to find some of your children waling in the truth, just as the Father commanded us (v 4). How well do you know the truth? How well are you walking in it? God wants you to be safe from false teachers. God wants you to be walking in the truth.