We know that whosoever is born of God If you suppose that God's children are wholly pure and free from all sin, as the fanatics contend, then the Apostle is inconsistent with himself; for he would thus take away the duty of mutual prayer among brethren. Then he says that those sin not who do not wholly fall away from the grace of God; and hence he inferred that prayer ought to be made for all the children of God, because they sin not unto death. A proof is added, that every one, born of God, keeps himself, that is, keeps himself in the fear of God; nor does he suffer himself to be so led away, as to lose all sense of religion, and to surrender himself wholly to the devil and the flesh. For when he says, that he is not touched by that wicked one, reference is made to a deadly wound; for the children of God do not remain untouched by the assaults of Satan, but they ward off his strokes by the shield of faith, so that they do not penetrate into the heart. Hence spiritual life is never extinguished in them. This is not to sin. Though the faithful indeed fall through the infirmity of the flesh, yet they groan under the burden of sin, loathe themselves, and cease not to fear God. Keepeth himself. What properly belongs to God he transfers to us; for were any one of us the keeper of his own salvation, it would be a miserable protection. Therefore Christ asks the Father to keep us, intimating that it is not done by our own strength. The advocates of freewill lay hold on this expression, that they may thence prove, that we are preserved from sin, partly by God's grace, and partly by our own power. But they do not perceive that the faithful have not from themselves the power of preservation of which the Apostle speaks. Nor does he, indeed, speak of their power, as though they could keep themselves by their own strength; but he only shews that they ought to resist Satan, so that they may never be fatally wounded by his darts. And we know that we fight with no other weapons but those of God. Hence the faithful keep themselves from sin, as far as they are kept by God. (John 17:11.)

We know that whosoever is born of God sinneth not - Is not habitually and characteristically a sinner; does not ultimately and finally sin and perish; cannot, therefore, commit the unpardonable sin. Though he may fall into sin, and grieve his brethren, yet we are never to cease to pray for a true Christian: we are never to feel that he has committed the sin which has never forgiveness, and that he has thrown himself beyond the reach of our prayers. This passage, in its connection, is a full proof that a true Christian "will" never commit the unpardonable sin, and, therefore, is a proof that he will never fall from grace. Compare the notes at Hebrews 6:4-8; Hebrews 10:26. On the meaning of the assertion here made, that "whosoever is born of God sinneth not," see the notes at 1-John 3:6-9.
Keepeth himself - It is not said that he does it by his own strength, but he will put forth his best efforts to keep himself from sin, and by divine assistance he will be able to accomplish it. Compare the 1-John 3:3 note; Jde 1:21 note.
And that wicked one toucheth him not - The great enemy of all good is repelled in his assaults, and he is kept from falling into his snares. The word "toucheth" (ἅπτεται haptetai) is used here in the sense of harm or injure.

Whosoever is born of God sinneth not - This is spoken of adult Christians; they are cleansed from all unrighteousness, consequently from all sin, 1-John 1:7-9.
Keepeth himself - That is, in the love of God, Jde 1:21, by building up himself on his most holy faith, and praying in the Holy Ghost; and that wicked one - the devil, toucheth him not - finds nothing of his own nature in him on which he can work, Christ dwelling in his heart by faith.

(17) We know that whosoever is born of God sinneth not; but he that is begotten of God keepeth himself, and that wicked one toucheth him not.
(17) A reason why not all, or rather why no sin is mortal to some: that is, because they are born of God, that is to say, made the sons of God in Christ, and being ended with his Spirit, they do not serve sin, nor are they mortally wounded by Satan.

We know that whosoever is born of God,.... Who is regenerated by his Spirit and grace, and quickened by his power; who has Christ formed in him, and is made a partaker of the divine nature, and has every grace implanted in him:
sinneth not; the sin unto death; nor does he live in sin, or is under the power and dominion of it, though he does not live without it; See Gill on 1-John 3:9;
but he that is begotten of God; the Vulgate Latin version reads, "the generation of God keeps or preserves him"; that is, that which is born in him, the new man, the principle of grace, or seed of God in him, keeps him from notorious crimes, particularly from sinning the sin unto death, and from the governing power of all other sins; but all other versions, as well as copies, read as we do, and as follows:
keepeth himself; not that any man can keep himself by his own power and strength; otherwise what mean the petitions of the saints to God that he would keep them, and even of Christ himself to God for them on the same account? God only is the keeper of his people, and they are only kept in safety whom he keeps, and it is by his power they are kept; but the sense is, that a believer defends himself by taking to him the whole armour of God, and especially the shield of faith, against the corruptions of his own heart, the snares of the world, and particularly the temptations of Satan:
and that wicked one toucheth him not; he cannot come at him so as to wound him to the heart, or destroy that principle of life that is in him, or so as to overcome and devour him; he may tempt him, and sift him, and buffet him, and greatly afflict and grieve him, but he can not touch his life, or hurt him with the second death; nay, sometimes the believer is so enabled to wield the shield of faith, or to hold up Christ the shield by faith, and turn it every way in such a manner, that Satan, who is here meant by the wicked one, because he is notoriously so, cannot come near him, nor in with him; cannot work upon him at all with his temptations, nor in the least hurt his peace, joy, and comfort: the saints know their perseverance from the promises of God and declarations of Christ; Psalm 125:1.

All mankind are divided into two parties or dominions; that which belongs to God, and that which belongs to the wicked one. True believers belong to God: they are of God, and from him, and to him, and for him; while the rest, by far the greater number, are in the power of the wicked one; they do his works, and support his cause. This general declaration includes all unbelievers, whatever their profession, station, or situation, or by whatever name they may be called. The Son leads believers to the Father, and they are in the love and favour of both; in union with both, by the indwelling and working of the Holy Spirit. Happy are those to whom it is given to know that the Son of God is come, and to have a heart to trust in and rely on him that is true! May this be our privilege; we shall thus be kept from all idols and false doctrines, and from the idolatrous love of worldly objects, and be kept by the power of God, through faith, unto eternal salvation. To this living and true God, be glory and dominion for ever and ever. Amen.

(1-John 3:9.)
We know--Thrice repeated emphatically, to enforce the three truths which the words preface, as matters of the brethren's joint experimental knowledge. This 1-John 5:18 warns against abusing 1-John 5:16-17, as warranting carnal security.
whosoever--Greek, "every one who." Not only advanced believers, but every one who is born again, "sinneth not."
he that is begotten--Greek aorist, "has been (once for all in past time) begotten of God"; in the beginning of the verse it is perfect. "Is begotten," or "born," as a continuing state.
keepeth himself--The Vulgate translates, "The having been begotten of God keepeth HIM" (so one of the oldest manuscripts reads): so ALFORD. Literally, "He having been begotten of God (nominative pendent), it (the divine generation implied in the nominative) keepeth him." So 1-John 3:9, "His seed remaineth in him." Still, in English Version reading, God's working by His Spirit inwardly, and man's working under the power of that Spirit as a responsible agent, is what often occurs elsewhere. That God must keep us, if we are to keep ourselves from evil, is certain. Compare John 17:15 especially with this verse.
that wicked one toucheth him not--so as to hurt him. In so far as he realizes his regeneration-life, the prince of this world hath nothing in him to fasten his deadly temptations on, as in Christ's own case. His divine regeneration has severed once for all his connection with the prince of this world.

Whosoever is born of God sinneth not. Does not live a life of sin. He will not sin unto death, though he may be overtaken in a fault. See note at end of chapter.
That wicked one toucheth him not. Cannot lay hands on him so as to hold him.
We know that we are of God. The church is God's temple in which he dwells, and around it the world of wickedness.
And we know that the Son of God is come. Not only by testimony from men but by God's witness. We have life in Christ, and Christ dwells in us.
This is the true God and eternal life. In Christ the true God is revealed to us and in him we have eternal life.
Keep yourselves from idols. Flee from idolatry, the besetting sin of that age. So too we need to flee from the idols of our age. Whatever takes our worship from God is an idol.

Yet this gives us no encouragement to sin: on the contrary, it is an indisputable truth, he that is born of God - That sees and loves God. Sinneth not - So long as that loving faith abides in him, he neither speaks nor does anything which God hath forbidden. He keepeth himself - Watching unto prayer. And, while he does this, the wicked one toucheth him not - So as to hurt him.