What does the Bible say about the transformation of believers?

In Philemon 11, Paul refers to Onesimus as having been 'unprofitable' but now 'profitable' to both himself and Philemon. This transformation signifies a fundamental change that occurs in the life of believers upon receiving Christ. Before conversion, individuals may have lived in selfishness and rebellion against God, rendering them unprofitable in spiritual terms. However, through faith in Jesus Christ, they become new creations, capable of good works that glorify God. This change reflects the heart of salvation—being called out of darkness into His marvelous light and into a life of service and love towards God and fellow believers.