How do we know that humans are incapable of saving faith?

The biblical doctrine of total depravity makes it clear that every individual, by nature, is spiritually dead in transgressions (Ephesians 2:1) and thus wholly incapable of taking any steps toward God without His initiating grace. Verses like Romans 3:10-12 assert that no one seeks after God, underscoring that the natural state of humanity is one of rebellion and spiritual death. The profound truth is that faith itself is a gift from God (Ephesians 2:8) that originates not from our will but from divine grace. John 3:3-7 emphasizes the necessity of being 'born again'—indicating that the exercise of faith is entirely contingent on this regenerative work of the Holy Spirit. Hence, any notion that pertains to the inherent ability of man to produce saving faith stands against the clear instruction of the Scriptures and the historic understanding of the Reformed faith.