The old formalisms of the law have become transformed into the new law.
1 Next, this must be considered. Since the sacraments of this visible kind got their efficacy from the passion of Christ and in some way represent it, they must be such as to be in harmony with the salvation wrought by Christ. Now, this salvation was promised, indeed, before Christ’s Incarnation and death but not displayed, it was the incarnate and suffering Word who brought about this kind of salvation.
Therefore, the sacraments which preceded Christ’s Incarnation had to be such as signified and somehow promised salvation. But the sacraments which follow the suffering of Christ ought to be such as deliver this salvation to men, not merely such as point to it by signs.
2 Of course, in this way one avoids the opinion of the Jews, who believe that the sacraments of the Law must be observed forever precisely because they were established by God, since God has no regrets and is not changed.
But without change or regret one who disposes things may dispose things differently in harmony with a difference of times; thus, the father of a family gives one set of orders to a small child and another to one already grown. Thus, God also harmoniously gave one set of sacraments and commandments before the Incarnation to point to the future, and another set after the Incarnation to deliver things present and bring to mind things past.
3 But more unreasonable still is the error of the Nazarenes and the Ebionites, who used to say that the sacraments of the Law should be observed simultaneously with those of the Gospel. An error of this kind involves a sort of contrariety.
For, while they observe the evangelical sacraments, they are professing that the Incarnation and the other mysteries of Christ have already been perfected; but, when they also observe the sacraments of the Law, they are professing that those mysteries are in the future.