Thus spake John Calvin:

We assert that the whole guilt of sin is taken away in baptism, so that the remains of sin still existing are not imputed […] There is a twofold grace in baptism, for therein both remission of sins and regeneration are offered to us. We teach that full remission is made, but that regeneration is only begun and goes on making progress during the whole of life.

Calvin wrote this in opposition to Trent’s tenth canon on baptism, which stated: “If anyone says that by the sole remembrance and the faith of the baptism received, all sins committed after baptism are either remitted or made venial, let him be anathema.”

So Calvin did not think this was a misleading accusation. He thought that the Roman Catholic Church had anathematized the Biblical doctrine.

Many years later, the great Protestant Scholastic teacher, Francis Turretin took the same ground against Rome.

Does baptism… take away past and present sins only and leave future sins to repentances? Or does it extend itself to sins committed not only before but also after baptism? The former we deny; the latter we affirm against the Romanists.…

II… [T]he Romansists teach… “The virtue of baptism does not reach to future sins, but the sacrament of penitence is necessary for their expiation.” Thus, the Council of Trent expresses it: “If anyone shall say that all the sins which are committed after baptism are either dismissed or made venial by the recollection of faith of the received baptism alone, let him be anathema (session 7, Canon 10, Schroeder, p. 54)….

XII. …However, we maintain that by baptism is sealed to us the remission not only of past and present, but also of future sins; still so that penitence (not a sacramental work and what they invent, but that which is commanded in the gospel) and especially saving faith is not excluded, but is coordinated with baptism as a divinely constituted means of our salvation (Francis Turretin, Institutes of Elenctic Theology, vol. 3).

Baptismal doctrine has, obviously, taken a weird turn since that time. Here is an essay I wrote that attempts to track some of that shift. A great place to read about the doctrine of the Westminster Confession on baptismal efficacy is in David F. Wright’s essay “Baptism at the Westminster Assembly.” It is in available in the first volume of The Westminster Confession into the 20th Century (ed., J. Ligon Duncan III, pp. 168-169). Of course, while the essay is worth the price of the book, you may not want to spend that much on an academic essay. If you want a more accessible, and less controversial book on baptism, consider buying my tract, Why Baptize Bapies: An Introduction to the Theology and Practice of the Reformed Churches.