A brief biography of Shepherd can be found here.  He was an important Congregational minister in early colonial America.

 

This passage from the works of Thomas Shepherd comes from a work in which he deals with the legality of the Sabbath.  In it, he implements an important distinction between the law as a rule, and the law as a covenant of works (a distinction that governs the formulations of the WCF, especially chapter 19).  He also deals with the issue of the covenant of works at Sinai.  As you might be able to tell, he is rather critical of the thesis propounded by the Calvinistic antinomians of the mid-17th century, who distinguished "the law given by the hand of Moses" and the "law given by the hand of Christ."

 

You can read it here. 

 

In this section he deals with the tough question of how Israel in the Old Testament are rightly said to be "under the law."  In my opinion, this is a rather standard, classic Reformed explanation.