Before the New Covenant circumcision was the mandatory physical sign established by God to confirm one’s justification, entrance into the marriage covenant and later the marriage covenant community. However, because of the superior form of justification and marriage gift offered under the New Covenant, both the sign and its requirement have changed. Baptism is now the mandatory physical sign which both replaces circumcision and improves upon it by the faith it requires, the superior form of justification it points to and the marriage gift of the New Birth and Holy Spirit it promises.
3.1. Circumcision was first established as a mandatory physical sign of God’s justification and covenant relationship with Abraham and his offspring (including the Israelites). It also represented their entrance into the covenant community of Israel (Gen 17:1-2, 10-14; Lev 12:3; Rom 4:11).
3.2. Baptism was established by Christ Himself after His justifying death and resurrection confirming its replacement of circumcision as the new mandatory physical sign of our justification before God and entrance into marriage covenant w/Him (Mat 28:18-19; Mar 16:16) .
3.3. Further confirmation that circumcision has been replaced is the fact that baptism is also considered the sign of our entrance into the covenant community of the church (Act 2:41).
3.4. Re: “…baptism as improving upon circumcision by:
3.4.1. The faith it requires (NAS: Act 8:36-37, 16:31-34; 1Pe 3:21. Improves: Jer 31:31-34).
3.4.2. The superior form of justification it points to: Payment Justification v. Passover Justification.
3.4.3. The marriage gift of the New Birth and Holy Spirit it promises.” (Joh 3:1-15; Eph 2:5-8; Eze 36:25-27; Jer 31:31-34;
 After Abraham, God’s marriage covenant only exists w/the covenant community and not the individual. This is clearly seen by the fact that spousal terminology is reserved for the nation of Israel and the church (e.g. Jer 31:32; Eph 5:22-24).
 Paedobaptists make a fatal flaw in this regard: b/c they fail to see the extent of soteriological change which has occurred under the New Covenant, they fail also to recognize that more has changed than just the sign. The “new circumcision” (i.e. baptism) is now of the heart rather than the flesh and requires faith (Col 2:11-12). Paedobaptists likewise miss the inconsistency created by their paradigm:
(OC) justification before covenant: babies in covenant by clean laws (i.e. circumcision).
(NC) covenant before justification: babies in covenant before clean law (i.e. faith in Christ).
Once considered, this truth strikes ironic in light of the fact that the strongest arguments made in favor of paedobaptists by its supporters is the consistency of their paradigm between these two covenants! It is only the Baptist position which truly preserves congruency between the covenants: (OC/NC) justification before covenant.
All of the signs which God has commanded that man observe function as mandatory in this way: Anyone unwilling to observe the sign—or to observe it correctly will not only fail to receive what it represents/symbolizes—but should also expect a curse (e.g. Exo 12:1-13; 1Co 11:27-30).
 In further support of baptism also being mandatory, consider that provision (not exception) is made for anyone unable but not refusing (Jam 5:14-15). Even the thief on the cross received a provisional form of baptism (through literal death and resurrection w/Christ!-Luk 23:43).
 See section entitled “Justification” for detailed discussion of the distinction between these two forms of justification. Consider also the fact that though Abraham’s justification came through faith and is therefore connected to those expressing faith under the New Covenant, he nonetheless received circumcision as the sign, since his was Passover and not Payment Justification.