How do we know that fleshly achievements do not contribute to salvation?

Paul's testimony illustrates that attempts to establish righteousness through fleshly achievements are ultimately worthless. In Philippians 3:7-8, he states that whatever he once regarded as gain, he now counts as loss for Christ. This indicates a fundamental understanding of salvation: it cannot be earned or improved by human efforts or merits. The peace and assurance come from recognizing that our standing before God is solely based on Christ’s righteousness, not our own. Therefore, fleshly achievements do not contribute to our salvation; they are a hindrance to it.