John Chrysostom

"But what kind of sin had these children," it may be said, "that they should do it away? for touching those who are of full age, and have been guilty of many negligences, one might with show of reason speak thus: but they who so underwent premature death, what sort of sins did they by their sufferings put away?" Didst thou not hear me say, that though there were no sins, there is a recompense of rewards hereafter for them that suffer ill here? …

Homily on the Gospel of Matthew 9 ↗

Theophylact of Ohrid

Then Herod, when he saw that he had been tricked by the Magi, was exceedingly wroth, and sent forth, and slew all the children that were in Bethlehem. As God used Moses to trick Pharaoh, so, too, He used the Magi to trick Herod. For both Herod and Pharaoh were child slayers: Pharaoh slew the male children of the Hebrews in Egypt, and Herod slew the male children of the Hebrews in Bethlehem. Herod vents his wrath against the Magi upon those who had wronged him in nothing. Why were the children allowed to be slaughtered? …

Commentary on Matthew ↗

Augustine of Hippo

And while he thus persecutes Christ, he furnished an army (of martyrs) clothed in white robes of the same age as the Lord. (Serm. 220. App.) Behold how this unrighteous enemy never could have so much profited these infants by his love, as he did by his hate; for as much as iniquity abounded against them, so much did the grace of blessing abound on them. (Serm. 373. 3.) O blessed infants! He only will doubt of your crown in this your passion for Christ, who doubts that the baptism of Christ has a benefit for infants. …

Catena Aurea by Aquinas ↗

Bede

In this death of the children the precious death of all Christ's martyrs is figured; that they were infants signifies, that by the merit of humility alone can we come to the glory of martyrdom; that they were slain in Bethlehem and the coasts thereof, that the persecution shall be both in Jerusalem whence the Church originated, and throughout the world; in those of two years old are figured the perfect in doctrine and works; those under that age the neophytes; that they were slain while Christ escaped, …

Catena Aurea by Aquinas ↗

Thomas Aquinas

Then Herod... Here he tells of the slaughter of the infants. In regard to this he does three things: first, the occasion of the slaughter is mentioned; secondly, the slaying (v. 16b); thirdly, the prophecies are quoted (v. 17). The occasion was Herod's anger; hence Herod was in a furious rage: "Man's anger does not work the justice of God" (Jas 1:20). And it should be noted that when a king suspects the loss of his kingdom, he quickly becomes inflamed with anger. …

Commentary on Matthew ↗