1 John 3:6

How can someone sin if he is not cut off from God in any way?

Everyone who remains in Him does not sin. To the extent he remains in Him, to that extent he does not sin.

And everyone who sins has neither seen Him nor known Him. He speaks of the vision and knowledge of faith, with which the righteous even in this life delight in seeing God, until they reach the very form of His open vision in the future, …

That is, one who unwaveringly follows after the virtues and never ceases to practice them.

Whosoever abideth in communion with him, by loving faith, sinneth not - While he so abideth. Whosoever sinneth certainly seeth him not - The loving eye of his soul is not then fixed upon God; neither doth he then experimentally know him - Whatever he did in time past.

Whosoever abideth in him,....

He sinneth not so long as he abideth in Christ. whosoever sinneth hath not seen him--Greek perfect, "has not seen, and does not see Him." Again the ideal of Christian intuition and knowledge is presented (Mt 7:23). All sin as such is at variance with the notion of one regenerated.

Whosoever abideth in him - See 1Jn 2:6. The word here employed (μένων menōn) properly means to remain, to continue, to abide. It is used of persons remaining or dwelling in a place, in the sense of abiding there permanently, or lodging there, and this is the common meaning of the word, Mat 10:11; Mat 26:38; Mar 6:10; Luk 1:56, “et saepe.” In the writings of John, however, it is quite a favorite word to denote the relation which one sustains to another, in the sense of being united to him, or remaining with him in affection and love; being with him in heart and mind and will, as one makes his home in a dwelling. The sense seems to be that we have some sort of relation to him similar to that which we have to our home; that is, some fixed and permanent attachment to him. We live in him; we remain steadfast in our attachment to him, as we do to our own home. For the use of the word in John, in whose writings it so frequently occurs, see Joh 5:38; Joh 6:56; Joh 14:10, Joh 14:17; Joh 15:27; 1Jn 2:6, 1Jn 2:10, 1Jn 2:14, 1Jn 2:17, 1Jn 2:27-28; 1Jn 3:6, 1Jn 3:24; 1Jn 4:12-13, 1Jn 4:15-16. In the passage before us, as in his writings generally, it refers to one who lives the life of a Christian, as if he were always with Christ, and abode with him. It refers to the Christian considered as adhering steadfastly to the Saviour, and not as following him with transitory feelings, emotions, and raptures. (See the supplementary note at Rom 8:10. We abide in Christ by union with him. The phrase expresses the continuance of the union; of which see in the note as above. Scott explains, “whoever abides in Christ as one with him and as maintaining communion with him. […]