How do we know that salvation is a work of the Spirit?

Salvation is fundamentally a mysterious work of the Holy Spirit, as seen in John 3:7-8, where Jesus explains that just as the wind blows where it pleases, so it is with those born of the Spirit. This underscores that salvation is not something we can engineer or comprehend; it is a divine act of mercy and grace. The Apostle Paul reiterates this in Romans 9:16, indicating that it does not depend on human desire or effort but on God who shows mercy. This highlights that our understanding and acceptance of the Gospel are purely the work of the Spirit in transforming hardened hearts into receptive ones.