Jerome

But the crowds that went before him and that followed him were shouting, saying, 'Hosanna to the Son of David! Blessings on the one who comes in the name of the Lord! Hosanna in the highest!' Let us now follow the spiritual order of discourse, for the story is clear. …

Commentary on Matthew ↗

Hilary of Poitiers

Is this the crowd who would applaud his crucifixion? How was their hatred earned from his grace? Even the words of their commendation pointed to the power of redemption. "Hosanna" in Hebrew signifies the redemption of the house of David. They are calling upon the Son of David. They are celebrating the inheritance of the eternal kingdom. They are proclaiming blessing in the name of the Lord. Soon their shouting of "Crucify him!" would be blasphemy. But at present, the deeds he was doing were exhibiting the form of the future. …

Commentary on Matthew 21.3 ↗

Thomas Aquinas

"And the multitudes that went before and that followed, cried out." Here is presented the honor exhibited to him in word. But by whom? By those going before and those following, namely, by those who were before the coming and after; and both seek salvation, and have it from Christ. 2 Cor 6:13: "Having the same recompense." The crowds were seeking salvation; hence they cried out saying: "hosanna to the Son of David" etc. This salvation is begun in the present, and will be perfected in the future. …

Commentary on Matthew ↗