John Calvin Commentary 1 Corinthians 15:9

"For I am the least of the apostles, that am not meet to be called an apostle, because I persecuted the church of God." — 1 Corinthians 15:9 (ASV)

For I am the least. It is not certain whether his enemies said this to detract from his credibility, or whether it was entirely on his own initiative that he made the acknowledgment. For my part, while I have no doubt that he was at all times voluntarily, and even cheerfully, disposed to abase himself so that he might magnify the grace of God, I suspect that in this instance he wished to counter slanders.

That some at Corinth aimed to detract from his dignity by malicious slander may be inferred not only from many previous passages, but also from his adding a little later a comparison (which he certainly would never have touched upon if he had not been compelled to it by the wickedness of some), to this effect: “Detract from me as much as you please—I will allow myself to be cast down below the ground; I will allow myself to be of no account whatever, so that the goodness of God towards me may shine forth all the more.”

“Let me, therefore, be reckoned the least of the Apostles; indeed, I acknowledge myself to be unworthy of this distinction. For by what merits could I have attained that honor? When I persecuted the Church of God, what did I merit? But there is no reason why you should judge me according to my own worth, for the Lord did not look at what I was, but by His grace made me an entirely different man.”

The sum is this: Paul does not refuse to be the most worthless of all, and next to nothing, provided this contempt does not hinder his ministry in any way and does not at all detract from his doctrine.

He is content, as for himself, to be considered unworthy of any honor, provided only that he upholds his apostleship on account of the grace conferred upon him.

And certainly, God had not adorned him with such distinguished endowments so that His grace might lie buried or neglected; rather, He had thereby designed to make his apostleship illustrious and distinguished.