John Murray

John Murray was a 20th century Reformed Theologian who taught at Westminster Theological Seminary in Philadelphia from 1937-1966.  He sought to develop Reformed theology in a variety of ways (including its doctrine of the covenant, the idea of the distinction between visible and invisible church, and the idea of "definitive sanctification").  Some of his views have been widely integrated into contemporary expressions of Reformed theology, while others are sharply disputed (sometimes rightly, but often unfairly). 
Recently, some have made the accusation that Murray was so inept as a theologian and exegete that he failed to write so much as a sentence on the letter to the Galatians.  It is true, that he did not write a full length commentary on Galatians (as he did on the Epistle to the Romans).  But the claim that he never dealt with the Epistle's teaching, particularly on the matter of the Mosaic law and the covenants, is patently false.
Not only are his published writings full of treatments of key texts from Galatians, he also devotes nearly two full lectures from his Systematic Theology course to an exegetical analysis of a key text in Galatians regarding the Law and the Covenants, namely, Gal. 3:17-22.  One may not agree with all of Murray's theology (or his exegesis, for that matter!).  But one cannot (in all Christian honesty and in good conscience) make the ridiculous accusation that he never taught or wrote on the letter.  One may not agree with his exegesis, but one cannot simply choose to ignore the fact that he lectured and published on it. 
For Murray's take on key texts in Galatians, look in the Scripture indices in his major published words (Redmption: Accomplished and Applied, Principles of Conduct, Commentary on Romans, etc).
His two class lectures dealing with Galatians 3 are available online here and here.  See the sub-page for a transcription of these lectures.