1 John 4:4-6

⁴ You are of God, little children, and have overcome them, because He who is in you is greater than he who is in the world.

⁵ They are of the world. Therefore they speak as of the world, and the world hears them.

⁶ We are of God. He who knows God hears us; he who is not of God does not hear us. By this we know the spirit of truth and the spirit of error.

you (v.4) — emphasized, in contrast to the false prophets. You, who are “of God.”

little children (v.4) — Children of God by faith in Christ

overcome (v.4) — refused to listen to or be influenced by. Christ has overcome the world (John 16:33), and believers are “in Christ.”

them (v.4) — the false prophets, the antichrists of verses 1 and 3.

He that is in you (v.4) — The power for victory lies, not in the child of God himself, but in the One who indwells him. The realization of this gives triumphant confidence in face of spiritual foes, confidence, not in self, but in God. See Zechariah 4:6; 1 Corinthians 15:57; Ephesians 6:10. “He that is in you” is the Holy Spirit; “he that is in the world” is the evil one, “the prince of this world” (John 12:31), “the god of this world” (2 Corinthians 4:4). — Vine, page 77.

they (v.5) — the false prophets, the antichrists. The word is emphasized.

they speak as of the world (v.5) — The character of their teachings is consistent with their evil origins, and what they teach meets with read reception on the part of those who belong to the same system. … There is stress upon the phrase “of the world”; the order in the original is “therefore of the world they speak.” The meaning is not that they speak concerning, or about, the world, but that the world is the element which characterizes their utterances. The same spirit energizes both teachers and hearers. — Vine, pages 77-78.

We (v.6, first usage) — the apostles

We are of God (v.6) — This is set in contrast with the statement in verse 5. … As, then, the one antichristian spirit energizes the false prophets and their words (v.5), so, on the contrary, the Holy Spirit energizes both the teachers of the truth and the children of God who are taught by them. — Vine, page 78

we (v.6, second usage) — emphasized

he who knows God (v.6) — lit. “he who habitually is getting to know God.”

The Apostle’s statement (v.6) plainly reveals his consciousness of the Divine authority imparted to him and to his fellow-apostles. It also implies the Divine inspiration of their writings. — Vine, page 78.

by this (v.6) — what he has just written

the spirit of truth, and the spirit of error (v.6) — The Spirit of truth is the Holy Spirit, as in John 14:17; 15:26; 16:13. … The phrase “the Spirit of truth” may describe either: (1) the source from whence He has proceeded, as sent from the Father (John 14:26) and from the Son (John 16:7), or (2) His character as the One who is truth, or (3) The One who communicates the truth (John 16:13-14); (2) and (3) are closely associated and together seem to convey what is intended. The spirit of error or of deceit, a phrase found [only here] in the New Testament is the spirit which is characterized by, and communicates error, which comes from him of whom the Lord said that “he is a liar and the father thereof” (John 8:44). … Those who are children of God learn to know the Spirit of truth and the spirit of error, according to the way in which any teaching conforms, or otherwise, to the teaching of the Apostles [for us today, Paul, the apostle to the Gentiles]. — Vine, pages 78-79.

Again, John was writing to Jewish kingdom believers who had/will have the law written on their hearts. He allowed no wiggle room for half-hearted, divided, unloving, carnally minded believers like those grace believers Paul addressed in 1 Corinthians 1:11; 3:1-4; 5:1-13; 6:1-8; and 2 Corinthians 12:20-21.