Writing on observation of the seventh day in the fourth commandment, Edward Leigh makes a comment on the covenant with Adam being the same as that made with Israel that might raise a few eyebrows. I have not read enough of Leigh to be sure exactly what he is saying, but I would be surprised if he was arguing that Mosaic economy was a covenant of works simpliciter, as opposed to the covenant of works being republished under Moses during the legal administration of the covenant of grace. If you know of anywhere else in Leigh where he addresses the question, please leave a comment. Here is the relevant extract: Indeed the Lord by a special institution given to Adam, Gen. 2. 1. had for the times before Christ appointed that they should reckon from the creation, which was the cause of that special institution; but this is no part of the Commandment; and in that institution God did two things: 1. He appointed the period from whence the seventh should be accounted, which else Adam according to the Law infused into him would have taken otherwise, for those ten were written in Adam’s heart, as is signified by the writing them in Tables of Stone, and calling them the Tables of the Covenant, for God did not make one Covenant with Israel another with Adam but one and the same with both. Indeed the Covenant made with Israel was put in the Ark, to shew Christ to be the end of the Law, but yet it was the same Covenant for matter, and so all the parts of it were written in Adam’s heart. Edward Leigh, A system or body of divinity consisting of ten books: wherein the fundamentals and main grounds of religion are opened, the contrary errors refuted, most of the controversies between us, the papists, Arminians, and Socinians discussed and handled, several Scriptures explained and vindicated from corrupt glosses: a work seasonable for these times, wherein so many articles of our faith are questioned, and so many gross errors daily published (London: William Lee, 1654), IX.V, p. 814.