John Calvin on Acts 9:21

21. They were all amazed. This is added, that we may know that the power of God was acknowledged. For seeing that the zeal of Paul against the gospel was openly known, they saw no other cause of such a sudden change but the hand of God. And, therefore, this is also one fruit of the miracle, that they all wonder at him being made a new man so suddenly, so that his doctrine doth the more move their minds. Whereas they say that he raged horribly with great cruelty, and that he came of late to Damascus that he might proceed in his purpose, these circumstances serve to augment the miracle. We must also note the phrase, those which call on his name, which withesseth that the godly did so profess the name of Christ, that they placed all their hope of salvation in him. According to that, these

“men put their trust in chariots, and others in horses, but we will call upon the name of the Lord,” (Psalm 20:7.)

Finally, whatsoever the Scripture commandeth concerning calling upon the name of God, it agreeth to the person of Christ.