:3 Daniel speaks of repentance and obeying God's voice as being a result of 'having discernment in thy truth' (Dan. 9:13,14 RV). To grasp the endless depth and height of the fact we are in touch with ultimate truth inevitably affects our lives. 3 Jn. 3 in the AV speaks of "the truth that is in thee"; but the Greek can also mean, as in the RV, "thy truth". To really believe true doctrine leads to repentance, and to our being truthful at the very least. Our contact with God's truth results in our being truthful not only to others but to ourselves, and this, as Daniel observed, gives rise to true repentance.

Paul can speak of “the word of the truth of the gospel” (Col. 1:5) and again of “the truth of the gospel” (Gal. 2:5). He refers to “the word of truth, the gospel of our salvation” (Eph. 1:13). It’s quite Biblical that we refer to our faith as “the truth”. But truth is clearly a way of describing or summing up the way of life which the doctrines of the truth should elicit in us. Thus “the new man... is created in righteousness and holiness of truth” (Eph. 4:24). We obey the truth in unfeigned love of our brethren (1 Pet. 1:22), not just by intellectual assent at a baptismal interview; we ‘do the truth’ in loving our brother (1 Jn. 1:6); if truth is in us then we walk in it (3 Jn. 3).

:7- see on 1 Pet. 4:14.

3 Jn. 7 refers to how the great preaching commission was obeyed: “For his name’s sake they went forth, taking nothing (material help) from the Gentiles" (Gentile believers). For the excellence of knowing His Name they went forth in witness, and moreover were generous spirited, not taking material help to enable this. The knowledge of the Name of itself should inspire to active service: for the sake of the Lord’s Name the Ephesians laboured (Rev. 2:3).

“The Gentiles” is put for ‘the Gentiles who believe’ (Rom. 2:14; 3 Jn. 7).

:10 A fair case can be made that he received the Apocalypse early, well before AD70, and wrote his gospel and letters afterwards. In this case, the similarity of wording would partly be explained by the fact that the language of his Lord rubbed off almost unconsciously [as well as consciously] upon John's style of thinking, speaking and writing. Thus "If I come, I will bring up the things he is doing" (3 Jn. 10) reflects the Lord's style: "If you do not repent, I will come to you" (Rev. 2:5). There are many other examples- finding them is good homework for the enthusiast. Now the practical point is surely that we are living the essence of the Kingdom life now; we ‘have eternal life’ in the sense that we are experiencing the nature and quality of the spiritual life which by grace we will eternally live. And that life is the life of the Lord Jesus; in His life on earth we see a picture of the nature of the eternal life which we hope to life for evermore. Therefore understanding Him personally is to understand the good news of the future Kingdom of God.

It is God's intention that "there should be no schism in the body" (1 Cor. 12:25). If we refuse to break bread with validly baptized, good living brethren- then we are working against God. And if we then go on to disfellowship anyone who will not agree with our opinion on a brother, we are doing just what Diotrephes is condemned for doing: "Diotrephes, who loveth to have the pre-eminence... receiveth us not... and not content therewith, neither doth he himself receive the brethren, and forbiddeth them that would, casting them out of the church" (3 Jn. 10,11).

:11 If we see / know God in the experiential sense, we will do no evil (3 Jn. 11). To have the true knowledge of Jesus Christ means we will not be barren [Gk. 'idle'] nor unfruitful (2 Pet. 1:8). When Zacharias wanted to have grounds for faith, he was simply told: "I am Gabriel...", the man like God (Lk. 1:19). The declaration of God's Name in Ex. 34:6,7 doesn't include statements like 'Trust in God! He'll help you!'. Instead we read of the grace, mercy, justice and inevitable judgment of God. Knowing and experiencing these more abstract things will lead us to a practical faith in God. Because David remembered God's Name, therefore He kept His law (Ps. 119:55 RSV). This is why the Bible uses the idea of 'knowing' God in the sense of knowing Him by experience, not just 'knowing' the right theory. Likewise John uses 'the truth' in the sense of not just correct knowledge but the way of life it brings forth.

:14 John records how the Lord called us friends (Jn. 15:5), and it is John who uses this title in addressing his brethren (3 Jn. 14). He reflected how the Lord saw him  as his friend. And John realised that this was how he should see his brethren; and so must we.