How do we know that doing good is a sign of being born of God?

In 3 John, John emphasizes that the one who does good is of God, indicating that good works are a manifestation of a believer's spiritual nature. This is rooted in the transformation that occurs through faith in Christ. True believers will not habitually practice sin, but rather will be inclined to good, reflecting the nature of God, who is inherently good. Thus, our good works serve not just as evidence of our faith, but also as an expression of our relationship with God, rooted in His grace and the empowering work of the Holy Spirit.