John Calvin Commentary Matthew 9:30

"And their eyes were opened. And Jesus strictly charged them, saying, See that no man know it." — Matthew 9:30 (ASV)

And Jesus threatened them. Either he wished to have other persons as witnesses of the miracle, or to delay its publication until another time. Their conduct in immediately proclaiming it everywhere is worthy of blame.

For the notion entertained by some, that Christ forbade them for the purpose of exciting them even more, has already been refuted. There was, no doubt, some reason for forbidding it, which is unknown to us; and those men, through inconsiderate zeal, spread the rumor before the proper time.