John Chrysostom — as excerpted in the Catena Aurea on Matthew 9:27-31

“And not for this reason only, but that He might make manifest that they were worthy of healing, and that none might object, that if mercy alone saved, then ought all to be saved. Therefore also He requires faith of them, that He may thereby raise their thoughts higher; they had called Him the Son of David, therefore He instructs them that they should think higher things of Him. Thus He does not say to them, Believe ye that I can ask the Father? But, Believe ye that I am able to do this? They say unto him, Yea, Lord. They call Him no more Son of David, but exalt Him higher, and confess His dominion. Then He lays His hand upon them; as it follows, Then he touched their eyes, saying, According to your faith be it unto you. This He says confirming their faith, and testifying that what they had said were not words of flattery. Then follows the cure, And their eyes were opened. And after this, His injunction that they should tell it to no man; and this not a simple command, but with much earnestness, And Jesus straitly charged them, saying, See that no man know it; but they went forth, and spread abroad the fame of him through the whole country.”