"Whoever makes a practice of sinning is of the devil, for the devil has been sinning from the beginning. The reason the Son of God appeared was to destroy the works of the devil. No one born of God makes a practice of sinning, for God's seed abides in him, and he cannot keep on sinning because he has been born of God." (1 John 3:8-9 ESV)
"This means that God's people in Christ, far from regarding sin with weary resignation or fearful foreboding, are assured that their struggle against it has both purpose and promise. Christ himself stands behind them as they wrestle with the forces and ideas and behavior against which John warns. The dramatic portrait of Christus victor dominates the literary horizon as the section comes to a close. The epistle's key counsel -- to abide in Christ and receive eternal life--is not a counsel of despair but a straightforward and compelling application of what Christ has already accomplished."
~ Robert Yarbrough, 1-3 John (Baker Exegetical Commentary), p. 189.
Painting above, a study of Nicodemus visiting Jesus, is by Henry Ossawa Tanner (1899).