3 John 1 “Elder” refers to John (see 2 John 1). John loves him with a truly Christian love. We should love others! Read 1 Corinthians 13:1-8.
3 John 2 Gaius is a very common name in the first century. John prays that Gaius’s physical health would prosper just like his spiritual health does. Gaius has trusted Christ and has a healthy soul. John prays that he would also be physically healthy. This is not a promise that he would be physically healthy, but it is his prayer. We should pray for others’ spiritual and physical health.
3 John 3-4 The “beloved” are Christians. Truth is mentioned three times in verses 3-4 (see also 3 John 1, 8, 12). John rejoices that they are walking/living in the truth. Verse five explains. A real source of joy for the Christian is to hear that others are living faithful Christian lives.
3 John 5 The example of walking/living in the truth that John gives is Gaius supporting the brethren, even when he does not know them. Christians practice real love toward each other. There is an invisible, eternal bond between believers, even when they are strangers.
3 John 6 Those brothers that Gaius supported, whom he didn’t know, came and told the church John was in. We, too, should spread encouraging news about others! John encourages Gaius to support the brethren even as they are leaving. This would include spiritual as well as financial support. Pray for and give to missionaries.
3 John 7 The reason John gives for supporting them this way is because they went out for Jesus’ sake and they did not accept anything from those to whom they were ministering (the Gentiles). Gentiles are non-Jews.
3 John 8 When we spiritually and financially support such men through prayers and giving, we are working together with the truth.
3 John 9-10 John goes from commending Gaius for his hospitality to condemning Diotrophes. He is a bad example of supporting the brethren. As the outline above indicates, his deeds include apostolic accusation, he doesn’t receive the brethren, he prevents others from receiving the brethren, and he exercises church discipline on those who receive the brethren. Unrepentant church leaders like this need to be confronted publicly because their sin is public.
3 John 11 John encourages Gaius not to imitate evil, but good. That is because doing good is of God. But the one who practices evil is not a true Christian. Be hospitable to the brethren!
3 John 12 Demetrius is an example of a true Christian who has a good testimony. He has a good testimony from 1) everyone, 2) from the truth, and 3) from the apostles. Strive to have a godly testimony.
3 John 13-15 John concludes his letter by explaining why his letter is so short. He hopes to see Gaius soon so that they can speak with one another. John wishes peace upon him and sends greetings from others and tells him to greet the brethren by their names, like the True Shepherd (John 10:3).