The account of the martyrdom of these children is given in the gospel of today. The Church justly honors them as martyrs, since they confessed Christ, if not by the mouth, yet by their death, which they suffered by reason of Herod's hatred against Christ.
The Introit of the Mass reads: "Out of the mouth of infants and sucklings Thou hast perfected praise, because of Thy enemies, O Lord. O Lord, how admirable is Thy name in the whole earth." Glory be to the Father, and to the Son, and to the Holy Spirit. As it was in the beginning, is now, and ever shall be, world without end. Amen.
O God, Whose praise the martyred innocents confessed on this day - not by speaking, but by dying - mortify in us all the evils of vices, that our life also may confess by actions Thy faith, which our tongue proclaims. Through Our Lord Jesus Christ, etc.
Epistle: Apocalypse 14:1-5
In those days I beheld a Lamb standing upon Mount Sion, and with Him an hundred forty-four thousand having His name, and the name of His Father written on their foreheads. And I heard a voice from heaven, as the noise of many waters, and as the voice of great thunder; and the voice which I heard was as the voice of harpers, harping on their harps. And they sung as it were a new canticle, before the throne, and before the four living creatures, and the ancients; and no man could say the canticle, but those hundred forty-four thousand, who were purchased from the earth. These are they who were not defiled with women, for they are virgins. These follow the Lamb whithersoever He goeth. These were purchased from among men, the first-fruits to God and to the Lamb; and in their mouth there was found no lie, for they are without spot before the throne of God.
Gospel: Matthew 2:13-18
At that time: An angel of the Lord appeared in sleep to Joseph, saying: Arise, and take the child and His Mother, and fly into Egypt; and be there until I shall tell thee; for it will come to pass that Herod will seek the child to destroy him. Who arose, and took the child and His Mother by night, and retired into Egypt; and he was there until the death of Herod, that it might be fulfilled which the Lord spoke by the prophet, saying: Out of Egypt have I called My Son. Then Herod perceiving that he was deluded by the Wise Men, was exceeding angry; and sending killed all the men-children that were in Bethlehem, and in all the borders thereof, from two years old and under, according to the time which he had dilligently inquired of the Wise Men. Then was fulfilled that which was spoken by Jeremias the prophet, saying: A voice in Rama was heard, lamentation and great mourning; Rachel bewailing her children, and would not be comforted, because they are not.
What persons are like Herod?
All those who destroy innocent children, in body or in soul, for example, imprudent and careless mothers who injure the fruit of their womb by excessive dancing, by heavy labor, by vehement anger or immoderate grief; unmanly men who are cruel to their wives while with child, who strike them, incite them to anger, or terrify them; heedless parents who neglect their little ones, who take them into bed at the risk of suffocating them, who do not take pains to keep them clean and healthy; those corrupt and godless women who destroy the fruit of their shame either before or after birth, and while yet unbaptized. But more cruel than all these, and even than Herod himself, are they who scandalize little children by impure conversations, by indecent songs, by acts of impurity in their presence, or by inciting them to the like; for thereby they plunge the souls of the children into destruction.
– Goffine's Devout Instructions