Here is the passage in the ESV: “In him also you were circumcised with a circumcision made without hands, by putting off the body of the flesh, by the circumcision of Christ, having been buried with him in baptism, in which you were also raised with him through faith in the powerful working of God, who raised him from the dead.”
In Greek: ἐν ᾧ καὶ περιετμήθητε περιτομῇ ἀχειροποιήτῳ ἐν τῇ ἀπεκδύσει τοῦ σώματος τῆς σαρκός, ἐν τῇ περιτομῇ τοῦ Χριστοῦ, 12συνταφέντες αὐτῷ ἐν τῷ βαπτισμῷ, ἐν ᾧ καὶ συνηγέρθητε διὰ τῆς πίστεως τῆς ἐνεργείας τοῦ θεοῦ τοῦ ἐγείραντος αὐτὸν ἐκ νεκρῶν:
The question for us is this: how connected are circumcision and baptism in this passage? The answer must be “very connected.” For example: the circumcision made without hands is epexegeted by verse 12’s “having been buried with him in baptism.” The circumcision of Christ at the end of verse 11 is also epexegeted by “baptism of Christ.” We know in other portions of Scripture that Jesus viewed His death as a baptism (Mark 10:38, where the present tense forbids us to understand His baptism there as the baptism that He experienced in the Jordan river). We also know that His death can be described as a cutting off (“circumcision”) for the sake of His people. Furthermore, we know that the New Covenant is in fundamental continuity with the Abrahamic Covenant (Galatians 3:7-9). So, in Colossians, Gentiles who have been baptized into Christ have already received the real circumcision. Now, some might attempt to argue that circumcision only has a pointing capacity (to Christ), and that therefore it ends with Christ’s finished work. However, here it is the Gentile (!) who is said to receive the circumcision, that is, that to which circumcision points. The significance, then, of circumcision is ongoing. The significance is that, in Christ’s circumcision, we receive that circumcision by being part of Christ’s body. How do we receive that circumcision? By being buried with Jesus in baptism. So, we receive that to which circumcision points by being baptized. Therefore, there is fundamental continuity between circumcision and baptism. Therefore, if anyone wishes to object to infant baptism, then those same objections have to be levelled against infant circumcision. This is part of John Calvin’s argument for infant baptism, by the way.