How can you tell if someone is a Christian? John gives a simple answer: “the one who does what is right is righteous, just as he [Christ] is righteous” (v. 7). We shouldn’t listen to anyone who tells us differently, such as the Gnostic teachers in John’s day, for if we do, they’ll lead us astray (v. 7; 1 John 2:26). Recognizing the difference isn’t rocket science, that is, it’s quite clear who belongs to Christ and who belongs to the devil (vv. 7–8). Followers of Christ walk in the light. They generally obey God’s commands, do what is right, and love one another. Unbelievers, by contrast, walk in darkness. They generally disobey the gospel, do what is evil, and fail to love others. They neither believe correctly about Christ, nor do they act correctly. Genuine believers in Jesus won’t continue to sin as a way of life (vv. 9–10). In fact, they can’t continue. Why not? Because they are not the same person. They’ve been reborn. They’re new creations (2 Cor. 5:17). In verse 9, “God’s seed” is a metaphor for salvation. Just as a man’s “seed” enters a woman and creates a new life, “God’s seed” enters our hearts by faith. The result is spiritual rebirth (John 3:3–7). And while the start of a new human life might miscarry, the start of a new spiritual life never fails. Regeneration cannot be reversed. Just as fallen human nature inevitably produces sin, so also does our redeemed nature inevitably produce righteousness. This is how we know that we’re children of God. “Only God sees the heart,” we sometimes say. Yes, but John taught that we can discern people’s spiritual conditions, including our own, from words and actions. A tree is known by its fruit. >> We’re not perfect yet, so regular confession of sin is an important spiritual discipline. But let us also rejoice that God’s love is transforming us into the image of His Son (Rom. 8:29)!