How do we know that believers are declared righteous by God?

The assurance of righteous standing before God comes from the biblical promise that those who believe in Jesus Christ receive the imputation of His righteousness. This is confirmed in Romans 4:5, which states that faith in Him justifies the ungodly. Furthermore, 2 Corinthians 5:21 explains that God made Christ, who knew no sin, to be sin for us, so that in Him, we might become the righteousness of God. Thus, our righteousness is rooted in the finished work of Christ, confirming that when one believes in Him, they are not only forgiven but are declared righteous in God's sight.