In his “Reformed View” chapter in Understanding Four Views on Baptism, Richard Pratt says,

The fact that there are two sacraments for the people of God in the NT age draws attention to a set of parallels in the OT. Baptism relates to circumcision, and the Lord’s Supper corresponds to Passover (65-66).

This connection between circumcision and baptism is typically based on Colossians 2:11-12: “In him you were also circumcised, in the putting off of the sinful nature, not with circumcision done by the hands of men but with the circumcision done by Christ, having been buried with him in baptism and raised with him through your faith in the power of God, who raised him from the dead.” NT believers undergo “the circumcision done by Christ’ as they are ‘buried with him in baptism” (66).

A connection between circumcision and baptism, however, is not as quick and simple as quoting Col. 2.11-12.  This passage refers to a not-done-by-hands circumcision, yet baptism (paedo- or credo-) is done with hands.  Also, this passage specifically states that we are buried in baptism and raised in faith – it is doubtful that Paul is mixing metaphors between ceremonial baptism and spiritual faith.  I’m not dogmatic about this, but my current understanding of these verses is that Paul is using water baptism as a concrete point of reference while actually basing his reasoning on the inner spiritual change that took place at conversion.

But even if Pratt’s take on Col. 2.11-12 were correct, or if we have other reasons to see parallels between circumcision and baptism, infant baptism is still not a necessary conclusion from the evidence.  I see the parallels between circumcision-baptism and Passover-Lord’s Supper as noticeable and accurate, but not Scripturally mandated.  In other words, the OT-NT relationship in these two areas is one of pattern/similarity and not type/anti-type.

In this sense, I’d agree entirely that baptism is a sign and seal of entrance into the covenant community.  It appears, however, that in their claim to “continuity,” the paedo-baptists are actually inconsistent on this point.  How did one join the covenant community in the OT?  Two ways: birth and proselytization.  In the NT, I’d say that entrance into the covenant community is still by birth – yet not by biological birth, rather by spiritual birth (Jn. 3.3-8; I Pet. 1.3).

Here is the paedo-baptist inconsistency: “OT circumcision is a physical sign of entering a physical community by physical birth, yet NT baptism is a spiritual sign of entering a spiritual community by physical birth.”  I prefer a more consistent parallel: baptism is a sign of entering the covenant by spiritual birth and thus, consistent with the NT examples, the sign should be taken by those who give testimony of being born  by the Spirit into God’s new covenant people.

As an aside, the argument is sometimes raised by credo-baptists that OT physical circumcision is replaced by NT heart circumcision (Rom. 2.29).  That argument omits the important factor that heart circumcision was even more important in the OT than the NT.  Circumcision of the heart is mentioned repeatedly across the entire spectrum of OT Scripture: Dt. 26.41; 10.12, 16; 30.6; Jos. 5.1; Jer. 4.4; 9.26; Ezk. 44.7, 9.  It is also noteworthy that NT heart circumcision is mentioned explicitly only in contexts addressed to Jews (Acts 7.51; Rom. 2.17-29).

Armstrong, John. Understanding Four Views on Baptism. Grand Rapids: Zondervan, 2007.