John Calvin Commentary 1 Corinthians 15:31

"I protest by that glorifying in you, brethren, which I have in Christ Jesus our Lord, I die daily." — 1 Corinthians 15:31 (ASV)

I die daily. He declares that he has such a contempt of death so that he might not seem to talk bravely when beyond the reach of danger. “I am every day,” he says, “incessantly beset with death. What madness would it be for me to undergo so much misery, if there were no reward reserved for me in heaven? Furthermore, if my glory and bliss lie in this world, why do I not rather enjoy them, than voluntarily resign them?” He says that he dies daily because he was constantly beset with dangers so formidable and so imminent that death, in a way, was hanging over him. A similar expression occurs in Psalm 44:22, and we will also find one of the same kind in the second Epistle (2 Corinthians 11:23).

By our glory. The old translation reads propter, (because of), but it has clearly arisen from the ignorance of transcribers, for in the Greek particle there is no ambiguity. It is, then, an oath by which he wished to arouse the Corinthians to be more attentive in listening to him when reasoning about the matter at hand. “Brethren, I am not some philosopher prattling in the shade. As I expose myself every day to death, it is necessary that I should think earnestly of the heavenly life. Believe, therefore, a man who is thoroughly experienced.”

It is also a form of oath that is not common but is suited to the subject at hand. Corresponding to this was that celebrated oath of Demosthenes, which is quoted by Fabius, when he swore by the Shades of those who had met death in the field of Marathon, while his object was to exhort them to defend the Republic. In the same way, Paul here swears by the glory which Christians have in Christ. Now that glory is in heaven. He shows, then, that what they questioned was a matter of which he was so certain that he was prepared to use a sacred oath—a display of skill that must be carefully noted.