Our Lord’s appearance to Saul of Tarsus (later called Paul) on the road to Damascus, changed the pitiless persecutor in a moment into the docile, yes the devoted follower of the Christ he had so bitterly hated.
This transformation took place not only because he had now seen the risen, ascended Christ; it was caused also by what he had learned from Christ. From heaven the Lord had revealed to Paul the glory of His finished work of redemption and had sent him forth to proclaim “the gospel of the grace of God” (Acts 20:24).
This is seen in the closing words of the Apostle’s first recorded sermon, delivered at the synagogue at Antioch in Pisidia. After mentioning the death and resurrection of Christ, the Apostle said:
“Be it known unto you therefore, men and brethren, that through this Man is preached unto you the forgiveness of sins; and by Him all that believe are justified from all things, from which ye could not be justified by the law of Moses” (Acts 13:38,39).
Paul never changed this message, but kept emphasizing it wherever he went as well as in his writings. He saw in this truth the answer to man’s condemnation for breaking God’s holy law. Thus he wrote to the Romans:
“…by the law is the knowledge of sin. But now the righteousness of God without the law is manifested” (Rom. 3:20,21).
“[We] declare, I say, at this time, [Christ’s] righteousness; that [God] might be just and the Justifier of him which believeth in Jesus” (Rom. 3:26).
Mark well: He does not say, “believeth and is baptized.” This was the message committed to the twelve (Mark 16:16; Acts 2:38). With the ushering in of the dispensation of grace, God was manifested as “the Justifier of him which believeth in Jesus.” source