What does the Bible say about the faithfulness of man?

According to Proverbs 20:6, most men will proclaim every one his own goodness. This highlights a natural inclination in humanity to self-justify and boast of personal merit. However, the challenge is presented in finding a truly faithful man, as faithfulness is not found among the sons of Adam. A true believer understands that any claim to goodness or merit before God is misguided, as revealed in Romans 7:18, which states that in the flesh dwells no good thing. Therefore, faithfulness is fundamentally rooted in recognizing one's utter reliance on God's grace and the righteousness of Christ, rather than self-proclamation.