How do we know what the doctrine of Christ truly is?

To understand the doctrine of Christ, one must turn to the Scriptures, which provide a clear revelation of who Jesus is. John emphasizes that the doctrine of Christ includes His incarnation, specifically the belief that He has come in the flesh. This teaching is foundational to the Christian faith because it is through the incarnation that God Himself bore the penalty for sin on behalf of His people. Denying any aspect of Christ's dual nature undermines the gospel's effectiveness and leads to a false understanding of salvation. Therefore, we must abide in the teaching of Christ as given in the Bible to ensure we possess the truth.