I am grateful to Christ Jesus our Lord, who has strengthened me, because he judged me faithful and appointed me to his service, even though I was formerly a blasphemer, a persecutor, and a man of violence. But I received mercy because I had acted ignorantly in unbelief, and the grace of our Lord overflowed for me with the faith and love that are in Christ Jesus. The saying is sure and worthy of full acceptance, that Christ Jesus came into the world to save sinners—of whom I am the foremost. But for that very reason I received mercy, so that in me, as the foremost, Jesus Christ might display the utmost patience, making me an example to those who would come to believe in him for eternal life. (1 Timothy 1:12-16, NRSV)
And I thank Christ Jesus our Lord, who hath enabled me, for that he counted me faithful, putting me into the ministry; Who was before a blasphemer, and a persecutor, and injurious: but I obtained mercy, because I did it ignorantly in unbelief. And the grace of our Lord was exceeding abundant with faith and love which is in Christ Jesus. This is a faithful saying, and worthy of all acceptation, that Christ Jesus came into the world to save sinners; of whom I am chief. Howbeit for this cause I obtained mercy, that in me first Jesus Christ might shew forth all longsuffering, for a pattern to them which should hereafter believe on him to life everlasting. (1 Timothy 1:12-16, KJV)
Paul's backstory might not look like much at first (he was beating up on Christians before he saw the light). But the Pastor sees it as evidence of just how far Paul's come. God brought Paul up out of the gutter and now he's put him on a pedestal to teach the truth. That's a pretty strong endorsement right there.