Jesus makes it absolutely clear to us in John 3:3 that we must be born again if we are to enter the kingdom of God and inherit eternal life (John 3:1–3). This means, as we have seen, that we are not children of God simply by our relation to other Christians. Instead, being “born again”—regeneration—is a spiritual reality. The Holy Spirit must change our hearts so that we can believe the gospel. We must receive living hearts of flesh to replace our stone hearts that are dead in Adam (Ezek. 11:19–20; Rom. 5:12–21).
Understanding that we must be born again by the Spirit of God does not mean that we know exactly how He accomplishes this aspect of our redemption. Much of the Spirit’s work in our lives is mysterious, in fact. We know the reality of the Holy Spirit, yet we cannot grasp all that He does. This is particularly true of the inner, invisible work of the Holy Spirit in our hearts. Jesus tells us as much in John 3:4–8, and especially in verse 8. Christ compares the movement of the Spirit to the blowing of the wind, an easy comparison for him to make, since the Hebrew word for “wind” (ruach) and the Greek word for “wind” (pneuma) are the same words used for “spirit.” The work of the pneuma, or “Spirit,” is like the pneuma, or wind, as both are invisible, largely unpredictable, and uncontainable.
Although we can see the effects of the wind in the bending of tree branches, the waving of tall grass, and the scattering of leaves, we cannot see the wind itself. That does not make the wind any less real or powerful. The same is true of the Holy Spirit. None of us can observe with our eyes the moment that He gives someone a new heart. No one can describe exactly how He does it. Still, we can observe the changes that the Spirit effects in a person.
The work of God the Holy Spirit can be seen most plainly in the spiritual fruit that He produces in the lives of His people (Gal. 5:22–23). Love, joy, peace, patience, kindness, goodness, self-control—these and more are what we see in people who have been born again. Not all the fruits are present in equal measure, but they are all present to some degree. When it comes to spiritual things, those who have not been born again produce no fruit. Moreover, the fruits we see are not perfect in this life, for sin remains until we are glorified (1 John 1:8–9). But the fruits are truly present. Evidences of these qualities in our lives provide objective proof of the subjective transformation effected in regeneration.