Feast of the Holy Name of Jesus
This is My Covenant which you shall observe, between me and you, and thy seed after thee in their generations: All the male kind of you shall be circumcised: And you shall circumcise the flesh of your foreskin, that it may be for a sign of the Covenant between Me and you.
An infant of eight days old shall be circumcised among you, every man child in your generations: he that is born in the house, as well as the bought servant shall be circumcised, and whosoever is not of your stock: And my covenant shall be in your flesh for a perpetual covenant (Gen. 17.10, 9,11-13).
Circumcision in the Old Testament was originally a rite of initiation to the life of the clan, Gen. 34.14-16. But in the above quoted passages, this circumcision of the flesh becomes the sign (like the rainbow, Gen. 9.16-17) to 'remind' God of His Covenant and man of his obligations deriving from his commitment to belong to God alone by membership in God's people. Thus, Abraham and his seed and their generations were to place themselves under the rule of the Lord as their King by obedience to His laws: The Lord thy God will circumcise thy heart, and the heart of thy seed: that thou mayst love the Lord thy God with all thy heart and with all thy soul (Deut. 30.6).
Note how the observance of the Covenant was not limited only to men who were already capable of making a protestation of faith. God's Covenant with Abraham extended -restricted* though it might be - to male infants of eight days old.
* At the time of Abraham, "faith was on the wane, many being given over to idolatry" (St. Thomas Aquinas, "Summa Theologica," III, Q. 70, Art. 2) and wallowing in the basest condition idolatry could ever offer man - where his natural reason was clouded by the vehemence of carnal concupiscence even in regard to sins against nature (as the crime of perversion of the men of Sodom, Gen. 13.13; Gen. 19.4-5). Therefore, the Lord instituted circumcision "as a profession of faith and a remedy against carnal concupiscence" (St. Thomas Aquinas, ibid.).
But as all things happened to the Fathers of Old in figure (1 Cor. 10.11), circumcision was therefore a sign (Gen. 17.10), "although less clearly figurative" (St. Thomas Aquinas, ibid., Art. 1), of Baptism. You are circumcised with circumcision not made by hand, in despoiling of the body of the flesh, but in the circumcision of Christ: buried with Him in baptism... (Col. 2.11). Both OT circumcision and Christian Baptism symbolize a renunciation of the flesh with its sins.
The objection offered therefore by the "Bible-only" sectarians, to wit, that infants are not capable yet of professing the faith to receive Baptism, is denied. They must hold also the imposition by God of circumcision, a sign of His Covenant, on infants as superfluous, if not absurd, for St. Paul teaches, circumcision profiteth indeed, if thou keep the law (Rom. 2.25).