John Calvin Commentary Matthew 28:17

"And when they saw him, they worshipped [him]; but some doubted." — Matthew 28:17 (ASV)

But some doubted. It is remarkable that, after they had twice seen Christ, still some doubted. If anyone chooses to view this as referring to the first appearance, there will be no absurdity in that opinion, for the Evangelists are sometimes in the habit of blending a variety of events.

However, it would also not seem absurd to suppose that, for some of them, the lingering effects of their former terror led them to hesitate again. We know that when Christ appeared, they were struck with fear and amazement until they had recovered their composure and had become accustomed to his presence.

The meaning, therefore, appears to me to be that some at first hesitated until Christ made a nearer and more familiar approach to them; but when they certainly and absolutely recognized him, then they worshipped, because the splendor of his divine glory was manifest. Perhaps it was this same reason that suddenly caused them to doubt and afterward led them to worship him: namely, that he had laid aside the form of a servant and had nothing in his appearance but what was heavenly.