How do we know that preaching the gospel saves people?

The preaching of the gospel is central to God's plan for salvation, as stated in Romans 1:16, where Paul declares that the gospel is the power of God for salvation to everyone who believes. It is through the foolishness of preaching that God chooses to reveal His truth, enabling individuals to hear and believe. Romans 10:17 affirms this by stating that faith comes by hearing, and hearing by the word of Christ. Thus, the faithful proclamation of the gospel is essential for salvation, as God uses these means to call His elect to Himself.