John Calvin on Acts 8:3

3. But Saul. We must note two things in this place, how great the cruelty of the adversaries was, and how wonderful the goodness of God was, who vouchsafed to make Paul a pastor of so cruel a wolf. For that desire to lay waste the Church wherewith he was incensed did seem to cut away all hope. Therefore his conversion was so much the more excellent afterward. And it is not to be doubted but that this punishment was laid upon him by God, after that he had conspired to put Stephen to death, together with the other wicked men, that he should be the ringleader of cruelty. For God doth oftentimes punish sins more sharply in the elect than in the reprobate.