1 John 5:18

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; ( Psalms 125:1 Psalms 125:2 ) ( Jeremiah 32:40 ) ( Matthew 16:18 ) ( John 10:28 ) .