I John 3:9

Whosoever is born of God--literally, "Everyone that is begotten of God." doth not commit sin--His higher nature, as one born or begotten of God, doth not sin. To be begotten of God and to sin, are states mutually excluding one another. In so far as one sins, he makes it doubtful whether he be born of God. his seed--the living word of God, made by the Holy Spirit the seed in us of a new life and the continual mean of sanctification. remaineth--abideth in him (compare Note, see on Jo1 3:6; Joh 5:38). This does not contradict Jo1 1:8-9; the regenerate show the utter incompatibility of sin with regeneration, by cleansing away every sin into which they may be betrayed by the old nature, at once in the blood of Christ. cannot sin, because he is born of God--"because it is of God that he is born" (so the Greek order, as compared with the order of the same words in the beginning of the verse); not "because he was born of God" (the Greek is perfect tense, which is present in meaning, not aorist); it is not said, Because a man was once for all born of God he never afterwards can sin; but, Because he is born of God, the seed abiding now in Him, he cannot sin; so long as it energetically abides, sin can have no place. Compare Gen 39:9, Joseph, "How CAN I do this great wickedness and sin against God?" The principle within me is at utter variance with it. The regenerate life is incompatible with sin, and gives the believer a hatred for sin in every shape, and an unceasing desire to resist it. "The child of God in this conflict receives indeed wounds daily, but never throws away his arms or makes peace with his deadly foe" [LUTHER]. The exceptional sins into which the regenerate are surprised, are owing to the new life principle being for a time suffered to lie dormant, and to the swo…

The apostle here magnifies the love of God in our adoption (Jo1 3:1, Jo1 3:2). He thereupon argues for holiness (Jo1 3:3), and against sin (v. 4-19). He presses brotherly love (Jo1 3:11-18). How to assure our hearts before God (Jo1 3:19-22). The precept of faith (Jo1 3:23). And the good of obedience (Jo1 3:24).

3:9-10 To live righteously means to live in a right relationship with God. (This is in contrast to the false teachers, who held that life in the spirit could not be contaminated by any behavior in a physical body.) This does not mean that we live perfect lives (1:8), but that we keep ourselves in a good relationship with God (1:9).