17 The people therefore that was with him when he called Lazarus out of his grave, and raised him from the dead, bare record.
[AD 407] John Chrysostom on John 12:12-19
(Hom. lxiv) The Law enjoined, that on the tenth day of the first month a lamb or a kid should be shut up in the house, and be kept to the fourteenth day of the same month, on the evening of which day it was sacrificed. In accordance with this law, the Elect Lamb, the Lamb without spot, when He went up to Jerusalem to be immolated for the sanctification of the people, went up five days before, i. e. on the tenth day.

(Hom. lxvi. 1) They showed now at last that they thought Him greater than a prophet: And went forth to meet Him, and cried, Hosanna! Blessed is the King of Israel, that cometh in the name of the Lord.

(Hom. lxvi. 1) This is what more than any thing made men believe in Christ, viz. the assurance, that He was not opposed to God, that He came from the Father. The words show us the divinity of Christ. Hosanna is, Save us; and salvation in Scripture is attributed to God alone. And cometh, it is said, not is brought: the former befits a lord, the latter a servant. In the name of the Lord, goes to prove the same thing. He does not come in the name of a servant, but in the name of the Lord.

(Hom. lxvi. 1) He did this prophetically, to figure the unclean Gentiles being brought into subjection to the Gospel; and also as a fulfilment of prophecy.

(Hom. lxvi. 1) Or thus: Whereas they had had wicked kings, who had subjected them to wars, He saith to them, Trust Me, I am not such as they, but gentle and mild: which He showed by the manner of His entrance. For He did not enter at the head of an army, but simply riding on an ass. And observe the philosophy (φιλοσοφίαν) of the Evangelist, who is not ashamed of confessing his ignorance at the time of what these things meant: These things understood not the disciple at the first, but when Jesus was glorified.

(Hom. lvi. 1) Our Lord had not then revealed these things to them. Indeed it would have been a scandal to them had they known Him to be King at the time of His sufferings. Nor would they have understood the nature of His kingdom, but have mistaken it for a temporal one.

(Hom. lxvi. 2) The world means here the crowd. This seems to be the speech of that part who were sound in their faith, but dared not profess it. They try to deter the rest by exposing the insuperable difficulties they would have to contend with.

[AD 430] Augustine of Hippo on John 12:12-19
(Tr. li. 7) The house was filled with the odour; the world was filled with the good fame.

(Tr. li. 1) See how great was the fruit of His preaching, and how large a flock of the lost sheep of the house of Israel heard the voice of their Shepherd: On the next day much people that were come to the feast, when they heard that Jesus was coming to Jerusalem, took branches of palm trees. The branches of palms are songs of praise, for the victory which our Lord was about to obtain by His death over death, and His triumph over the devil, the prince of death, by the trophy of the cross.

(Tr. li. 2) Hosanna is a simple exclamation, rather indicating some excitement of the mind, than having any particular meaning; like many interjections that we have in Latin.

(Tr. li. 4) It were a small thing to the King eternal to be made a human king. Christ was not the King of Israel, to exact tribute, and command armies, but to direct souls, and bring them to the kingdom of heaven. For Christ then to be King of Israel, was a condescension, not an elevation, a sign of Hispity, not an increase of His power. For He who was called on earth the King of the Jews, is in heaven the King of Angels.

(Tr. li. 5) John relates the matter briefly, the other Evangelists are more full. The ass, we read in them, was the foal of an ass on which no man had sat: i. e. the Gentile world, who had not received our Lord. The other ass, which was brought, (not the foal, for there were two,) is the believing Jew.

(Tr. li) This act of our Lord's is pointed to in the Prophets, though the malignant rulers of the Jews did not see in it any fulfilment of prophecy: As it is written, Fear not, daughter of Sion, behold thy King cometh sitting on an ass's colt. Yea, in that nation though reprobate, though blind, there remained still the daughter of Sion; even Jerusalem. To her it is said, Fear not, acknowledge Him whom thou praisest, and tremble not when He suffers. That blood it is which shall wipe away thy sins, and redeem thy life.

(Tr. li) i. e. When He showed the power of His resurrection, then they remembered that these things were written of Him, and that they had done these things unto Him, i. e. those things that were written of Him.

(Tr. li. 7) The crowd was disturbed by the crowd. (Turba turbavit turbam) But why grudgeth that blind crowd, that the world should go after Him, by Whom the world was made?

[AD 735] Bede on John 12:12-19
It is a compound of two words; Hosi is shortened into save; Anna a mere exclamation, complete. Blessed is He that cometh in the name of the Lord. The name of the Lord here is the name of God the Father; though we may understand it as His own name; inasmuch as He also is the Lord. But the former sense agrees better with the text above, I am come in My Father's name. (5:43) He does not lose His divinity, when He teaches us humility.

[AD 1107] Theophylact of Ohrid on John 12:12-19
The Jews, when they called Him King of Israel, dreamed of an earthly king. They expected a king to arise, of more than human greatness, who would deliver them from the government of the Romans. But how did our Lord come? The next words tell us; And Jesus when He had found a young ass, sat thereon.

(non occ.) See then the consequences of our Lord's passiona. It was not to no purpose that He had reserved His greatest miracle for the last. For the resurrection of Lazarus it was that made the crowd believe in Him. The people therefore that was with Him when He called Lazarus out of his grave, and raised him from the dead, bare record. For this cause the people also met Him, for that they heard that He had done this miracle. Hence the spite and plotting of the Pharisees: The Pharisees therefore said among themselves, Perceive ye how ye prevail nothing? behold the world is gone after Him.

As if they said, The more you attack Him, the more will His power and reputation increase. What use then of these attempts?

[AD 407] John Chrysostom on John 12:17
For so many would not have been suddenly changed, unless they had believed in the miracle.
[AD 428] Theodore of Mopsuestia on John 12:17-18
Since through Adam death came, which subjected everyone, they had heard through their prophets and believed that death would be defeated. When they saw that this had been done by our Lord, who raised a man dead for four days, they took branches of palm trees and went out to meet him as the victor over death, which oppresses humankind, and praised him with appropriate hymns. Since the Pharisees did not like this, they reproached them by saying that they followed him in vain, but it was their reproach that was in vain, since all the people went after him anyway.

[AD 444] Cyril of Alexandria on John 12:17-18
The gathering of the common people, having heard what had happened, were readily persuaded by those who had witnessed that the Christ had raised Lazarus to life and annulled the power of death, as the prophets said. This is why they too went and met him.

[AD 1022] Symeon the New Theologian on John 12:17
So tell me, where did you learn that you did not belong to those who are foreknown and predestined to become conformed to the image of God’s glory? Tell me, who told you this? Was it, maybe, God Who announced this to you, Himself, or by one of His prophets, or through an angel? “No,” you say, “but I do suppose that I am not predestined to salvation, and that all my effort would be in vain.” And why do you not believe instead with all your soul that God has sent His only-begotten Son on the earth for your sake alone, and for your salvation, that He knew you beforehand and predestined you to become His brother and co-heir? Why are you not eager to love Him with all your heart and to honor His saving commandments? Why do you not rather believe that, having been slaughtered for your sake, He will never abandon you, nor allow you to perish? Do you not hear Him saying: “Can a woman forget her suckling child . . . yet I will not forget you” [Isaiah 49:15]? So, if by anticipation you judge yourself unworthy, and willfully separate yourself from the flock of Christ’s sheep, you should understand that it is none other than you who are the cause of your own damnation.

Therefore, casting out of our souls all faithlessness, sloth, and hesitation, let us draw near with all our heart, with unhesitating faith and burning desire, like slaves who have been newly purchased with precious blood. Indeed, with reverence for the price paid on our behalf, and with love for our Master Who paid it, and as having accepted His love for us, let us recognize that, if He had not wished to save by means of Himself us who have been purchased, He would not have come down to earth, nor would He have been slain for our sake. But, as it is written, He has done this because He wills that all should be saved. Listen to Him say it Himself: “I did not come to judge the world, but to save the world” (John 12:17). - "Second Ethical Discourse"
[AD 1107] Theophylact of Ohrid on John 12:17
The Evangelist is saying that the people who saw the miracle which He worked for Lazarus were witnesses and heralds of His power. This is why He was met with glory by the people who had heard, that is, believed, that He had done this miracle. If they had not believed, they would not have congregated so swiftly.