Gerhard's exposition of Christ's active obedience has some really insightful commentary. In particular, the way that he addresses the fact that such an idea was universally adopted by Lutherans, but not by the Reformed, is quite enlightening.

Essentially, many Reformed argue that as a man, Jesus is obligated to fulfill the law for his own sake, rather than vicariously for the sake of others. This point is also made by Anselm.

But, Gerhard argues that the communicatio idiomatum makes such a position untenable.

At the incarnation, the divine authority/glory of the Logos is also the property of the human nature. Therefore, as Lord of the Law, Jesus does not owe obedience to the Law for his own sake. Rather, his coming *under* the Law necessitates its being done for the sake of the other.

As his infinitude is united to all acts in the Mediatorial office, the obedience of Christ during the humiliation is necessarily infinite, and thus universal, in scope.