Deep study
Acts and the Epistles - the persecutor turned apostle of grace
If grace can save Saul of Tarsus, it can save anyone. Paul's life is the gospel in miniature.
Saul was a Pharisee's Pharisee - circumcised the eighth day, blameless under the law, and so zealous that he hunted Christians to prison and death (Philippians 3:4-6; Acts 8:3). He had every religious credential a man could want. Later he would call all of it loss for the sake of Christ. Religious zeal, he learned, is no substitute for knowing Christ.
On his way to arrest believers, a light from heaven flattens him and a voice asks, Saul, Saul, why are you persecuting me? (Acts 9:4). Jesus identifies Himself with His people - to touch the church is to touch Him. In an instant the persecutor is undone, not by argument but by the risen Christ. Grace seized him before he sought it - the clearest proof that salvation begins with God, not us.
Paul's letters hammer one truth: a person is justified by faith in Jesus Christ and not by works of the law (Galatians 2:16). In Romans 3 he shows that all have sinned, and that God justifies freely by His grace through the redemption in Christ - so that God is both just and the justifier of the one who has faith in Jesus (Romans 3:26). The verdict of righteousness is a gift, received by faith, never a wage earned by performance.
Paul was given a thorn in the flesh. Three times he begged for its removal, and the Lord answered, my grace is sufficient for you, for my power is made perfect in weakness (2 Corinthians 12:9). Paul then boasts in his weaknesses, that Christ's power may rest on him. The apostle of grace learned grace in his own frailty.
Paul always points away from himself: by the grace of God I am what I am (1 Corinthians 15:10). He calls himself the foremost of sinners, saved as an example of Christ's perfect patience (1 Timothy 1:15-16).
And his gospel stretches from a Damascus road all the way to the renewal of all things. The whole creation, he says, groans together in the pains of childbirth, waiting to be set free (Romans 8:22-23) - and that longing is answered in John's vision, where God will wipe away every tear, and death shall be no more (Revelation 21:4). The grace that justified the chief of sinners is the same grace that will one day fill a new heaven and new earth. Paul's life simply says: look not at me, but at the Christ who saved even me, and who is making all things new.