2 John 1:10-13

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.

¹² Having many things to write to you, I did not wish to do so with paper and ink; but I hope to come to you and speak face to face, that our joy may be full.

¹³ The children of your elect sister greet you. Amen.

If (v.10) — assumes a fact —  these men will come

comes (v.10) — not coming as a visitor but as a teacher

this doctrine (v.10) — the doctrine of Christ, that He is God in the flesh (v.7)

do not receive him (v.10) — This excludes all manner of welcome. The injunctions are a faithful prohibition against compromising the truth. For a professed teacher, who is actually a propagator of an error which strikes at a foundation truth of the faith, and therefore is not a Christian, to be received into a believer’s house as if the errorist was himself a believer, firstly, is disloyalty to Christ, secondly, makes it possible for him to do incalculable harm to the saints, thirdly, tends to establish him in his false teaching, and fourthly, means personal fellowship in the evil by condoning false doctrine (v.11). … Fidelity to Christ demands obedience to the commands here given, and forbids the slightest toleration of both the teachings and the teachers. Love of the truth involves hatred of error. — Vine, page 119.

deeds (v.11) — should be the stronger “works”

paper (v.12) — A sheet of paper made of strips of papyrus, which was abundant in the Nile and was formed into a material for writing. — Vine, page 120.

come to you (v.12) — lit. “to become (i.e., be) with you — more than company, it indicates enjoyment.

John was not telling believers to avoid non-believers or believers who have mistaken views. But believers should avoid those who hold fast to their false views, attempt to convince others, and refuse to consider the truth. This would include pastors and teachers who do not teach the true gospel, and, if believers aren’t supposed to even greet these false teachers warmly or allow them into their homes, then they should obviously also avoid going to listen to them in church. Loyalty should be to the message, not to the assembly or the individual.