Drew Mery [5 min. readout] provides us with a quote from Alan Conner’s book, “Covenant Children Today: Physical or Spiritual?“, on the crucial point in the debate over infant baptism and covenant membership:
Covenant Membership the Key Issue
The general view set forth in these Confessions [i.e Heidelberg Catechism; Second Helvetic Confession; Westminster Confession of Faith] is that the infants of believers are in the New Covenant, are members of the church, and therefore, should be baptized. If this principle of infant membership is found in the New Covenant, then infant baptism has a strong ally. But, if the New Covenant presents a different principle of membership, one based on personal faith in Christ and actually possessing the blessings of the New Covenant, then infant baptism comes up against a powerful foe. Without the principle of infant membership, the view of infant baptism expressed in the Confessions above would suffer a major and perhaps irrecoverable blow.
New Wine in Old Wineskins?
Credobaptists believe that baptizing infants based on the principle of membership in the Old Covenant is similar to the faulty practice of trying to ‘pour new wine into old wineskins.’ The concept of membership in the New Covenant cannot be poured back into the old worn out wineskins of the Old Covenant. We believe that those who practice infant baptism do not take seriously enough that the New Covenant is, in fact, a ‘New’ Covenant, not like the Old Covenant (Jeremiah 31:31-32). We affirm that there are important elements of both continuity and discontinuity [added emphasis] between the Old and New Covenants. Yet, the practice of infant baptism is based upon a mistaken view of continuity in the area of covenant membership.
We also believe that the principle of membership taught in the New Covenant is at the heart of its essential ‘newnewss.’ No longer is membership in the New Covenant defined by the genealogical principle of the Old Covenant. For, as Paul taught, ‘be sure that it is those who are of faith who are sons of Abraham’ (Galatians 3:7) and ‘it is not the children of flesh who are children of God, but the children of the promise are regarded as descendants’ (Romans 9:8). These ‘children of promise’ are determined not by physical lineage, but by the sovereign choice of God who chooses Isaac over Ishmael and Jacob over Esau (Romans 9:9-13). The New Covenant ‘children of God’ are not those ‘born of blood, nor of the will of the flesh, nor of the will of man, but of God’ (John 1:12-13). Thus, Old Covenant membership was based on physical birth, whereas in the New Covenant it is based exclusively on spiritual birth from above (John 3:3,5).
If these convictions are true to the teachings of the Bible, then membership in the New Covenant is restricted to those who have faith, and they alone should receive the covenant sign of baptism. This is a clear departure from membership in the Old Covenant, but it is one made necessary by the fact that new wine requires new wineskins.