“While an examination of the entirety of the work [“The Necessity of Reforming the Church”] would be beneficial, for our purposes we only need to focus on Calvin’s discussion regarding the reforming of worship. While justification by faith alone has a primary role in the Reformation, Calvin actually gives worship the place of preeminence.
If it be inquired, then, by what things chiefly the Christian religion has a standing existence amongst us and maintains its truth, it will be found that the following two not only occupy the principal place, but comprehend under them all the other parts, and consequently the whole substance of Christianity, viz., a knowledge first, of the mode in which God is duly worshiped, and, secondly, of the source from which salvation is to be obtained (Calvin, Necessity, 126).
“It’s not hard to understand Calvin’s thinking here. The worship of God is that which has been commanded, by God. It’s that which his people are to engage in, faithfully, day in and day out. To get worship wrong is to get the Christian faith wrong. We are redeemed to worship the Lord” (“Less Outward Glory: An Examination of Calvin’s Reformation of Worship” by Everett A. Henes in The Confessional Presbyterian, Vol. 13, 122-123).