Summary: Those who are twice-born reveal divine parentage through life, through confidence and through victory.
“We know that everyone who has been born of God does not keep on sinning, but he who was born of God protects him, and the evil one does not touch him.” 
Some truths cannot be hidden. Though an evil individual may attempt to hide the evil that contaminates the soul, the sinful proclivity becomes increasingly obvious as people come to know that individual. Jesus taught, “From within, out of the heart of man, come evil thoughts, sexual immorality, theft, murder, adultery, coveting, wickedness, deceit, sensuality, envy, slander, pride, foolishness. All these evil things come from within, and they defile a person” [MARK 7:21-23]. What we are internally, we reveal outwardly.
Similarly, a godly person will be recognised as godly through that person’s conduct. Again, this truth becomes obvious from what the Master taught. Perhaps you recall Jesus’ words, “The good person out of the good treasure of his heart produces good, and the evil person out of his evil treasure produces evil, for out of the abundance of the heart his mouth speaks” [LUKE 6:45]. Daily routines expose what lies in the heart.
No individual is perfect; no person lives without sin. Likewise, even people we identify as evil may show some good qualities on occasion. No good person is one hundred percent good; and no evil person is absolutely evil. On occasion, bad people may do good deeds; even Al Capone organised soup kitchens for hungry people. I have likewise witnessed some powerful preachers who could be petty and heartless toward people with whom they disagreed.
In the context of what has already been presented, sinless perfection, the idea that an individual can live such a holy life that they no longer sin, is popular among some segments of the Faith. Though the concept may appear attractive, it is unattainable in this present life. The Apostle to the Gentiles was unaware of the possibility of living without struggles against sin. You may recall his lament recorded in his Letter to Roman Christians.
“I do not understand my own actions. For I do not do what I want, but I do the very thing I hate. Now if I do what I do not want, I agree with the law, that it is good. So now it is no longer I who do it, but sin that dwells within me. For I know that nothing good dwells in me, that is, in my flesh. For I have the desire to do what is right, but not the ability to carry it out. For I do not do the good I want, but the evil I do not want is what I keep on doing. Now if I do what I do not want, it is no longer I who do it, but sin that dwells within me.
“So, I find it to be a law that when I want to do right, evil lies close at hand. For I delight in the law of God, in my inner being, but I see in my members another law waging war against the law of my mind and making me captive to the law of sin that dwells in my members. Wretched man that I am! Who will deliver me from this body of death” [ROMANS 7:15-24]?
To be sure, we who name the Name of Christ are to strive for holiness; we are to work to live a life marked by devotion to God, a life that is separated from sin. Without question, the Christian has the Spirit of God living within to empower him. However, we struggle to be holy because the old nature is yet very much a part of life. Otherwise, there would be no need of the repeated admonitions to bring our life into conformity with the will of the Lord. Yet, for the Christian, the trajectory of life is always toward the light.