The Great Commentary of Cornelius à Lapide
Matthew 21:16
And said unto Him, hearest Thou what these say? And Jesus saith unto them, Yea; have ye never read, out of the mouth of babes and sucklings thou hast perfected praise? (Psalms 8:3.) The Hebrew is ימדת עז iissadta oz, i.e., hast founded strength. Aquila, hast laid foundations, power; Sixtine edition, Thou hast constituted strength; Tertuilian (Lib. de anima, cap. 19), Thou hast furnished praise; Syriac, Thou hast directed praise; Arabic, Thou hast prepared praise. This is, Thou hast proved, confirmed, made Thy power perfectly laudable, when out of the mouth of infants, not having the use of their tongues, and not yet able to give utterance, or to speak, Thou dost express Thy praise and glory. For thou hast caused that on Palm Sunday infants with the people should cry out to Christ, Hosanna to the Son of David. S. Hilary, and Auctor Imperfecti, understand by infants boys already able to speak and give utterance. With more truth S. Chrysostom, Euthymius, and Theophylact think that these were really infants unable to speak, as it is here expressly said. Whence the Syriac translates, Out of the mouth of little boys and infants Thou hast directed praise; and therefore Luke adds (Luke 19:40) that Christ said, If these should be silent the stones will cry out. By this was signified that the infants equally with the boys being moved and acted upon by a Divine instinct and miracle, cried Hosanna to Christ, though they did not understand the word, yea although the infants naturally were not yet able to speak it. The reason was that which the Psalmist subjoins (Psa 8:3), "That Thou mayest destroy the enemy and the avenger," that in truth, through the mouths of infants Thou mayest confound the Scribes and Pharisees, the enemies of Christ, and mayest teach that they are senseless, and more foolish than infants, for these acknowledge, praise, and glorify Jesus as Christ. But those latter words of the psalm Christ did not cite, intentionally, lest He should too greatly exasperate the Scribes. At the same time, Christ here intimates that infants should be early taught, as soon as they begin to speak, to utter pious words that their first words should be Hosanna, Jesus, Mary, &c. Thus S. Jerome writes to Blæsilla, that she should teach her little daughter Paula, the grandchild of her grandmother, S. Paula, as soon as she began to speak, to utter and pronounce Alleluia. So our S. Francis Borgia was taught when an infant to utter as his first words, Jesus, Maria, as Ribadaneira testifies in his life. Thus the Trisagion, for example, Holy, Holy, Holy, Lord God of Sabaoth, was revealed to a boy caught up into the air at the time of an earthquake at Constantinople, which ceased as soon as the people, instructed by the boy, cried the Trisagion, A.D, 446, in the time of the Emperor Theodosius, as Damascene testifies (Trad de Trisagis). For God delights in the praises of boys, for boys (pueri) are so called from purity (puritate), says Varro, because they are not yet come to years of puberty, and are pure like terrestrial angels.
Arias Montanus (in Psalm ii.) observes, that infants in all nations utter the word יה, iah, which is the Name of God, and an abbreviation of Jehovah; and thus God claims for Himself the commencement and foundations of His wonderful Name, firmly uttered by the very mouth of infants. In like manner, Arnobius asserts that there is no man whatsoever who has not entered upon the first day of his life with the idea of God; and that the brutes, the trees, and the stones would cry out, if they were able to speak, that God is the Lord of all things. So Plato (lib. 10, de Republ.) and Cicero (lib. 1, de Natura Deorum) teach that we share in the knowledge and praise of God with our mother's milk. Lyra distinguishes a threefold order of children praising God. The first are those who praise God by their deaths, not with their mouths; such as the Innocents who were slain by Herod for Christ's sake. The second, such as praise with their mouths rather than by their deaths, like those who sang Hosanna to Christ. The third, those who both by their mouths and their deaths praised God. Such were S. Agnes, thirteen years of age; S. Pancras, twelve; SS. Vitus, Celsus, and others. See our Philip Barlaymont (in Paradiso puerorum, cap. 13 and 14), where he recounts the praises and oracles of God uttered by the mouths of infants.
Observe: the eighth Psalm seems to be spoken literally of God's magnificence which He shows in the creation of the universe in which He made man the lord of all things. Yet more appropriately and profoundly, according to the letter, it speaks of the magnificence of God which He manifests in the re-creation and redemption of the world, in which He has made Christ the conqueror of death and sin, and the Redeemer of the world, and the Lord of all things; who therefore is the First Man, and the most noble of all men. This is plain 1. Because Christ here so expounds it, as S. Paul does (Heb 2:7). 2. Because such great magnificence as the Psalmist there celebrates does not apply so well to the misery of man-who, after his fall into sin, lost his dominion over the brutes as it does to Christ. 3. Because this passage, "Out of the mouths of infants and sucklings Thou hast perfected praise," applies much more clearly and truly to Christ than to any others. A like passage is Deuteronomy 18:18, as I have there said. For as to Maldonatus explaining it of David calling himself (in respect of Goliath, whose head he cut off) an infant, it is certain that he was not literally an infant at that time, but a spirited and warlike youth. Whence Nicephorus (on Psalms 8) says: "The Incarnation of the W ORD is the magnificence of God."