1 John 3:9 No one who is born of God practices sin, because His seed abides in him; and he cannot sin, because he is born of God.
Here the apostle John is not teaching the heresy of sinless perfectionism. However, he is teaching the trajectory of the Christian life in sanctification leads to overcoming one sin after another, not remaining in it or boasting in it. Here his argumentation is consistent with the apostle Paul (Romans 6) and the words of the blessed Lord Jesus Christ (Mark 9:42-50). The Christian is in the business of killing sin by the power of the Holy Spirit, bearing fruit in keeping with repentance, or overcome by sin and thus demonstrating that he is not a Christian at all.~Doron Gladden