And he that keepeth his commandments He confirms what I have already stated, that the union we have with God is evident when we entertain mutual love: not that our union begins thereby, but that it cannot be fruitless or without effect whenever it begins to exist. And he proves this by adding a reason, because God does not abide in us, except his Spirit dwells in us. But wherever the Spirit is, he necessarily manifests his power and efficiency. We hence readily conclude, that none abide in God and are united to him, but those who keep his commandments. When, therefore, he says, and by this we know, the copulative, and, as a reason is here given, is to be rendered, "for," or, "because." But the character of the present reason ought to be considered; for though the sentence in words agrees with that of Paul, when he says that the Spirit testifies to our hearts that we are the children of God, and that we through him cry to God, Abba, Father, yet there is some difference in the sense; for Paul speaks of the certainty of gratuitous adoption, which the Spirit of God seals on our hearts; but John here regards the effects which the Spirit produces while dwelling in us, as Paul himself does, when he says, that those are God's children who are led by the Spirit of God; for there also he is speaking of the mortification of the flesh and newness of life. The sum of what is said is, that it hence appears that we are God's children, that is, when his Spirit rules and governs our life. John at the same time teaches us, that whatever good works are done by us, proceed from the grace of the Spirit, and that the Spirit is not obtained by our righteousness, but is freely given to us.

And he that keepeth his commandments - See the notes at John 14:23.
And hereby we know that he abideth in us - That is, this is another certain evidence that we are true Christians. The Saviour had promised John 14:23 that he would come and take up his abode with his people. John says that we have proof that he does this by the Spirit which he has given us. That is, the Holy Spirit is imparted to his people to enlighten their minds; to elevate their affections; to sustain them in times of trial; to quicken them in the performance of duty; and to imbue them with the temper and spirit of the Lord Jesus. When these effects exist, we may be certain that the Spirit of God is with us; for these are the "fruits" of that Spirit, or these are the effects which he produces in the lives of men. Compare the notes at Galatians 5:22-23. On the evidence of piety here referred to, see the notes at Romans 8:9, Romans 8:14, Romans 8:16. No man can be a true Christian in whom that Spirit does not constantly dwell, or to whom he is not "given." And yet no one can determine that the Spirit dwells in him, except by the "effects" produced in his heart and life. In the following chapter, the apostle pursues the subject suggested here, and shows that we should examine ourselves closely, to see whether the "Spirit" to which we trust, as furnishing evidence of piety, is truly the Spirit of God, or is a spirit of delusion.

Dwelleth in him - i.e. in God; and he - God, in him - the believer.
And hereby we know - We know by the Spirit which he hath given us that we dwell in God, and God in us. It was not by conjecture or inference that Christians of old knew they were in the favor of God, it was by the testimony of God's own Spirit in their hearts; and this testimony was not given in a transient manner, but was constant and abiding while they continued under the influence of that faith that worketh by love. Every good man is a temple of the Holy Ghost, and wherever he is, he is both light and power. By his power he works; by his light he makes both himself and his work known. Peace of conscience and joy in the Holy Ghost must proceed from the indwelling of that Holy Spirit; and those who have these blessings must know that they have them, for we cannot have heavenly peace and heavenly joy without knowing that we have them. But this Spirit in the soul of a believer is not only manifest by its effects, but it bears its own witness to its own indwelling. So that a man not only knows that he has this Spirit from the fruits of the Spirit, but he knows that he has it from its own direct witness. It may be said, "How can these things be?" And it may be answered, By the power, light, and mercy of God. But that such things are, the Scriptures uniformly attest, and the experience of the whole genuine Church of Christ, and of every truly converted soul, sufficiently proves. As the wind bloweth where it listeth, and we cannot tell whence it cometh and whither it goeth, so is every one that is born of the Spirit: the thing is certain, and fully known by its effects; but how this testimony is given and confirmed is inexplicable. Every good man feels it, and knows he is of God by the Spirit which God has given him.

And he that keepeth his commandments dwelleth in him, and he in him. And hereby we know that he abideth in us, by the (f) Spirit which he hath given us.
(f) He means the Spirit of sanctification, whereby we are born again and live to God.

And he that keepeth his commandments,.... Attends to those instructions and declarations concerning faith in Christ, and love to the brethren, and acts according to them:
dwelleth in him, and he in them; that is, he dwells in Christ, and Christ dwells in him; the same is said of believing in Christ under the figurative expressions of eating his flesh, and drinking his blood; see Gill on John 6:56;
and hereby we know that he abideth in us; or dwelleth in us, as before,
by the Spirit which he hath given us; which if understood of private Christians, as the preceding verses incline to, the sense is, that union to Christ, and the continuance of it, or his indwelling as a fruit of union, and the permanency of that, are evidenced by the Spirit of God; who is given in consequence of union and relation to Christ, as a spirit of regeneration and sanctification, of faith and love, of adoption, and as the earnest of the heavenly inheritance; but if of the apostles and ministers of the word, it may regard the gifts of the Holy Spirit bestowed on them, fitting them for their work and office, and who is a spirit of truth, and not of error; and by having and enjoying these, they knew that Christ abode in them, and had reason to believe, according to his promise, that he would be with them, and with his ministering: servants in succession, to the end of the world; and this sense seems to be encouraged by the former part of the following chapter.

dwelleth in him--The believer dwelleth in Christ.
and he in him--Christ in the believer. Reciprocity. "Thus he returns to the great keynote of the Epistle, abide in Him, with which the former part concluded" (1-John 2:28).
hereby--herein we (believers) know that he abideth in us, namely, from (the presence in us of) the Spirit "which He hath given us." Thus he prepares, by the mention of the true Spirit, for the transition to the false "spirit," 1-John 4:1-6; after which he returns again to the subject of love.

And he that keepeth his commandments - That thus believes and loves. Abideth in him, and God in him: and hereby we know that he abideth in us, by the Spirit which he hath given us - Which witnesses with our spirits that we are his children, and brings forth his fruits of peace, love, holiness. This is the transition to the treating of the Holy Spirit which immediately follows.