John Calvin Commentary 1 Corinthians 15:15

"Yea, we are found false witnesses of God; because we witnessed of God that he raised up Christ: whom he raised not up, if so be that the dead are not raised." — 1 Corinthians 15:15 (ASV)

We are also found to be false witnesses. The other disadvantages, it is true, which he has just recounted, were more serious regarding us—that faith was made vain, that the whole doctrine of the gospel was useless and worthless, and that we were deprived of all hope of salvation. Yet this also was no trivial absurdity: that the Apostles, who were ordained by God to be the heralds of his eternal truth, were found to have deceived the world with falsehoods. For this brings the highest dishonor to God.

The expression, false witnesses of God, we may understand in two ways: either that by lying they used the name of God under a false pretext, or that they were found to be liars in testifying to what they had received from God. The second of these I rather prefer, because it involves a crime that is much more heinous, and he had spoken previously concerning men. Now, therefore, he teaches that if the resurrection of Christ is denied, God is made guilty of falsehood in the witnesses that have been brought forward and hired by him. The reason, too, that is added, corresponds well—because they had declared what was false, not from themselves, but from God.

I am at the same time well aware that there are some who give another rendering to the particle κατά. The old interpreter renders it against. Erasmus, on the other hand—concerning. But, as it also has among the Greeks the force of ἀπό (from), this meaning seemed to me to be more in accordance with the Apostle’s design. For he is not speaking here of the reputation of men (as I have already stated), but he declares that God will be exposed to the charge of falsehood, since what they publish has come from him.