Circumcision compared to Baptism
We know that all who were circumcised were not believers –
Rom. 2:28, 29: “For he is not a Jew, which is one outwardly; neither is that circumcision which is outward in the flesh: but he is a Jew, which is one inwardly; and circumcision is that of the heart, in the spirit, and not in the letter; whose praise is not of men, but of God.”
There were many who did not confess their sins and walked contrary to the will of God. They received punishment due to it.
Lev. 26:40, 41: “If they shall confess their iniquity and the iniquity of their fathers, with their trespass which they trespassed against me, and that I also have walked contrary unto them, and have brought them into the land of their enemies; if then their uncircumcised hearts be humbled, and they then accept of the punishment of their iniquity.”
Knowing that not all those who receive the circumcision will be believers, Lord gave the sign of circumcision even unto infants.
Old Covenant: Circumcision
Deut. 10:16: “Circumcise, therefore, the foreskin of your heart and be no more stiffnecked.”
Deut. 30:6: “And the Lord thy God will circumcise your heart and the heart of your seed to love the Lord thy God with all your heart and with all your soul, that you may live.” .
Jer. 4:4: “Circumcise yourselves to the Lord and take away the foreskin of your heart, ye men of Judah and inhabitants of Jerusalem.”
New Covenant: Baptism
Acts 2:38: "Then Peter said unto them, Repent and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost
Act 22:16: “And now, why tarriest thou? arise, and be baptized and wash away thy sins, calling on the name of the Lord.”
Rom. 6:4: “Therefore, we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we should walk in newness of life.”
Gal. 3 :28: “For as many of you as have been baptized into Christ have put on Christ.”
Paul actually equates them in the following passages:
Col. 2:11, 12: “In whom also ye are circumcised with the circumcision made without hands, in putting off the body of the sins of the flesh by the circumcision of Christ; buried with him in baptism, whereas also ye are risen with him through the faith of the operation of God, who hath raised him from the dead.” .
Phil. 3 :3: “For we are the circumcision which worship God in the spirit and rejoice in Christ Jesus, and have no confidence in the flesh.”
Paul notes that baptism has replaced circumcision referring to baptism as "the circumcision of Christ" and "the circumcision made without hands." Of course, it was mainly infants who were circumcised under the Old Law; circumcision of adults was rare. If Paul, in making this parallel, meant to exclude infants from baptism, he would have said so.