How does God ensure the character of His witnesses?

God guarantees the integrity of His witnesses by transforming them through His grace. In 2 Corinthians 1:12, Paul notes that he conducted himself in simplicity and godly sincerity, which is a result of God's grace working in him. This change of heart and character occurs through the new birth, granting believers a nature that seeks to glorify God. As seen in Romans 6, believers are no longer slaves to sin but are empowered by God's Spirit to walk in accordance with His will, ensuring that their testimony aligns with the truth of the gospel.