How do we know that salvation is not based on free will?

Biblical doctrine supports that humans in their natural state are incapable of choosing God due to total depravity, as indicated in Romans 3:10-12, which states that there is none who seeks God. The notion that one can exercise free will to achieve salvation contradicts the clear teachings of scripture that highlight God's initiative and grace in saving those He has chosen. Salvation is a work of God alone, as reflected in Ephesians 2:8-9, where it states, 'For by grace you have been saved through faith, and that not of yourselves; it is the gift of God, not of works, lest anyone should boast.' Therefore, true faith in Christ is a response to God's prior work in the hearts of His elect.