How do we know that salvation cannot be earned by works?

Scripture clearly indicates that no amount of human effort can secure salvation. Isaiah 64:6 states, 'All our righteousnesses are as filthy rags,' illustrating that our best attempts fall short of God's glory. Romans 3:23 confirms that all have sinned and fall short of the glory of God. Therefore, salvation must be received by faith through grace, as emphasized in Ephesians 2:8-9, which declares it is not of works, lest anyone should boast. This doctrine underscores the heart of sovereign grace theology—that we are saved solely through God's merciful initiative.