Baptism
Colossians 2:11-12
In whom also you are circumcised with circumcision not made by hand... buried with him in baptism, in whom also you are risen again by the faith of the operation of God, who hath raised him up from the dead.
Context of the passage
Paul warns the Colossians against false teachers who demanded Mosaic circumcision, explaining that baptism has replaced circumcision as the sign of entry into the covenant.
Catholic reading
Paul explicitly presents baptism as the New Covenant counterpart to Old Covenant circumcision; since circumcision was administered to Jewish infants on the eighth day as covenant entry, this parallel supports the Church's practice of baptizing infants into the New Covenant.
Common objection
Baptism here is spiritual 'circumcision of Christ' accomplished by faith, meaning only believers capable of faith, not infants, can receive this spiritual reality.
Response
The passage speaks of the faith of the believing community and God's operative power as the ground of this new circumcision, and just as physical circumcision was administered to infants incapable of personal faith yet still truly entered them into the covenant, so too infant baptism, administered in the faith of the Church, truly incorporates the child into Christ.