2 John 9–11 (NKJV)
9 Whoever transgresses and does not abide in the doctrine of Christ does not have God. He who abides in the doctrine of Christ has both the Father and the Son. 10 If anyone comes to you and does not bring this doctrine, do not receive him into your house nor greet him; 11 for he who greets him shares in his evil deeds.
Today is the first Sunday of Christmas – a glorious opportunity to continue celebrating the Incarnation of Jesus. John’s words today remind us that the Incarnation of Jesus is not just an interesting fact of history that is relatively unimportant; rather it is the reality that shapes the very meaning of the name “Christian.”
Truth matters. Hence, to reject the “doctrine of Christ” – by which John means the reality of the Incarnation, that the Word of God, He who was in the beginning with God and was God, took on human flesh and dwelt among us – is to reject God Himself. Those who profess faith in “God” but who reject God’s Son do not worship God but an idol. They may be sincere; they may be kind; they may be gracious; but they are not worshipers of the true and living God.
John insists on the inseparability of the Father and the Son. We cannot have the Father without the Son; nor can we have the Son without the Father. Jesus Himself declared, He who does not honor the Son does not honor the Father who sent Him” (Jn 5:22-23). Consequently, John forbids us from recognizing as brethren those who deny Jesus. If anyone comes to you and does not bring this doctrine, do not receive him into your house nor greet him; for he who greets him shares in his evil deeds.
As you may know, Wheaton College was in the news a couple weeks ago for indefinitely suspending a professor for declaring that Muslims and Christians worship the same God. This action by Wheaton’s president Philip Ryken was encouraging. Like the Docetists whom John is addressing, Muslims worship an idol, they do not worship the Living God. Sura 4.171 in the Koran declares,
O followers of the Book! do not exceed the limits in your religion, and do not speak (lies) against Allah, but (speak) the truth; the Messiah, Isa son of Marium is only an apostle of Allah and His Word which He communicated to Marium and a spirit from Him; believe therefore in Allah and His apostles, and say not, Three. Desist, it is better for you; Allah is only one God; far be It from His glory that He should have a son, whatever is in the heavens and whatever is in the earth is His, and Allah is sufficient for a Protector.
According to Islam, therefore, Jesus is not God. How then is it possible to confess in any meaningful way that Muslims and Christians worship the same God? One can only do so by repudiating the “doctrine of Christ” and ceasing to be a Christian in any meaningful sense. Allah is an idol; Yahweh is the Living God.
John’s words again remind us that we are called upon to worship the Jesus who has revealed Himself in history; we are to worship and serve the Jesus of revelation not the Jesus of our imagination. And this means drawing lines, making distinctions, and saying – what you are teaching is false.

As we come into the presence of God this day, therefore, we are summoned to come into His presence only in the Name of His Son Jesus, for there is one Mediator between God and men, the Man Christ Jesus. And reminded that truth matters, let us confess that we are often afraid to stand for truth and against error. And let us kneel as we confess our sins together.