4 Everyone who makes a practice of sinning also practices lawlessness; sin is lawlessness. 5 You know that he appeared in order to take away sins, and in him there is no sin. 6 No one who abides in him keeps on sinning; no one who keeps on sinning has either seen him or known him. 7 Little children, let no one deceive you. Whoever practices righteousness is righteous, as he is righteous. 8 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. 9 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. 10 By this it is evident who are the children of God, and who are the children of the devil: whoever does not practice righteousness is not of God, nor is the one who does not love his brother.
Notice that John starts his maxim with “Everyone”. This is in fact all inclusive. If (much like the 3 class conditional statements) the shoe fits wear it. Don’t forget in the previous sections closing “And everyone who thus hopes in him purifies himself as he is pure.” John is wanting us to notice the contrast of the pure from the sinner. “Practicing” (poiōn) as we will soon study, reveals our true nature or perhaps the lack of a new nature. As Akin comments “John makes an obvious contrast between this construction (pas ho poiōn tēn hamartian, “everyone who practices sin” [NASB]) and the expression in 2:29 (pas ho poiōn tēn dikaiosunēn, “everyone who practices righteousness” [NASB]). Not only does the child of God live a life marked by righteousness (2:29) and purity (3:3), but he abstains from a life characterized by the practice of sin. The word poiōn is used frequently in this section (vv. 3, 4, 7, 8, 9, 10) to imply a continual practice of sin as well as a realization of sin’s completeness. In other words, it is a willful, habitual action.”

John previously has established in 1:8 that if we claim to be without sin we are a liar. He is not telling you a different story he is merely explaining our true beliefs are revealed in our consistent actions. Johns’ address in vs 7 “Little children let no one deceive you” should bring out the foghorn of what he’s addressing. The gnostic influence not only had bad theology but their bad theology is always revealed in their bad lifestyles. Much like Jesus address in John 8 accusing the Pharisees to be sons of the devil, John does not hesitate to call out those who do the works of the devil are of the devil (see John 8:44 and 2Cor 4:4). John goes on to explain that the reason the Son of God appeared was to destroy the works of the Devil. The works of the devil are revealed in what we do. So many times in Scripture it is clear it Jesus makes a clear distinction between what we say and what we do (see Matt 7:21 and James 1:22 not to mention the Behma seat judgment or the white throne judgment). What we do ultimately reflects what we believe. Being born of God reveals that what we do does not reveal our ability to perform but reveals what only God can do. If it’s not happening…God didn’t do it. What we do as in practicing righteousness and loving our brother come with the sanctification package.