"The opinion of the Reformed with their reasons
The Reformed assert that there absolutely is a covenant of works, because: (1) it is expressly mentioned in Hosea 6:7, וְהֵמָּה כְּאָדָם עָבְרוּ בְרִית שָׁם בָּגְדוּ בִי, “And they, like Adam, have transgressed the covenant; there they have dealt faithlessly with me” (cf. Job 31:33). There the best translators—the Vulgate, the Zurich Bible, Pagnino, Castellio, the Dutch translators, and others—render כאדם not appellatively, but properly, although, I confess, there are not lacking those who prefer to render it appellatively. (2) The apostle in Galatians mentions two covenants (4:24), the first of which is from the works of the law (2:16), demanding the most exact obedience (3:10), by aid of which no one has ever achieved life (2:16; 3:11), under which we all were, until the covenant of faith (3:23), and are, as long as we exist as children of the flesh (3:22, 29), a covenant which only produces slavery (3:24 with Heb. 2:14–15). And this is the very covenant that we call the covenant of works; the latter covenant is from the faith of the gospel. If you should say that the apostle is not speaking about the covenant in paradise, but about the covenant at Sinai, it may easily be responded that the apostle is speaking about the covenant in paradise insofar as it has been repeated and renewed at Sinai with Israel in the Decalogue, which had the content of the covenant of works. (3) Synonyms for the covenant of works are evident in the New Testament (Rom. 3:27 and Gal. 2:16). Moreover, what is the “law of works” if not the covenant of works? What is “law” simply speaking, insofar as it is opposed to grace? (Rom. 8:3) What, I say, if not a legal covenant? For we are said to be not under law, but under grace (Rom. 6:14–15; 4:16), and what is this, if not that we are not under a legal covenant? At the least these are to us entirely synonymous. (4) We have already demonstrated in the exegetical part that all the essentials of the covenant of works are contained in its first promulgation (Gen. 2:17). (5) We can hardly secure very many heads of the Christian religion sufficiently—such as the propagation of original corruption, the satisfaction of Christ, and his subjection to the divine law (Rom. 8:3–4; Gal. 3:13; 4:4–5)—when the covenant of works is denied."
(Theoretical-Practical Theology vol.3, Mastricht, Rester & Beke, Pg. 441, eBook, The Elenctic Part.)