Matthew 21:3

He said not to His disciples, Say, Thy Lord, or Your Lord, hath need of them; that they may understand, that He is Lord alone, not of the beasts only, but of all men; for even sinners are by the law of nature His, though by their own will they are the Devil's. it is to be understood, that after He had entered into Jerusalem, the beast was returned by Christ to its owner.

But as it was then said to the Apostles, If any man say ought to you, say ye, The Lord hath need of them; so now it is commanded to the preachers, that though any opposition be made to them, they should not slack to preach.

(ap. Anselm) Or, The owner of the beasts will straightway send them to be engaged for Christ's service.

Whence also, when He ascended into heaven, He gave command to His disciples that they should loose sinners, for which also He gave them the Holy Spirit. But being loosed, and making progress, and being nourished by the Divinity of the Word, they are held worthy to be sent back to the place whence they were taken, but no more to their former labours, but to preach to them the Son of God, and this is what He signifies when He says, And straightway He will send them.

And yet He had often entered Jerusalem before, but never with so much circumstance. What then is the cause? It was the beginning then of the dispensation; and neither was He very well known, nor the time of His passion near; wherefore He mixed with them with less distinction, and more disguising Himself. For He would not have been held in admiration, had He so appeared, and He would have excited them to greater anger. But when He had both given them sufficient proof of His power, and the cross was at the doors, He makes Himself then more conspicuous, and doeth with greater circumstance all the things that were likely to inflame them. For it was indeed possible for this to have been done at the beginning also; but it was not profitable nor expedient it should be so. But do thou observe, I pray thee, how many miracles are done, and how many prophecies are fulfilled. He said, "Ye shall find an ass;" He foretold that no man should hinder them, but that all, when they heard, should hold their peace. But this is no small condemnation of the Jews, if them that were never known to Him, neither had appeared before Him, He persuades to give up their own property, and to say nothing against it, and that by His disciples, while these, being present with Him at the working of His miracles, were not persuaded.