From Ursinus’s Commentary on the Heidelberg Catechism, a collection of his teaching notes compiled principally by David Paraeus, we have this explanation of religious “ceremonies” and their permissibility in worship. This is included under the discussion of the Fourth Commandment:

III. HOW MANY KINDS OF CEREMONIES ARE THERE?

There are two kinds of ceremonies some that are commanded by God himself; and others that are instituted by men. Ceremonies which have been instituted by God, are such as constitute his worship, and can only be changed by God himself. Sacrifices, by which we offer and render obedience to God, are ceremonies of this sort, being divinely instituted. So the sacraments, by which God testifies and bestows his benefits upon us, are also divinely instituted. Ceremonies instituted by the church are not the worship of God, and may be changed by the advice of the church, if there are sufficient causes to demand a change.

IV. IS IT LAWFUL FOR THE CHURCH TO INSTITUTE CEREMONIES?

The church may and ought to institute certain ceremonies, inasmuch as the moral worship of God cannot be observed without defining and fixing the various circumstances connected with it. We may, therefore, say that it is proper for the church to institute ceremonies when the following conditions are observed: 1. They must not be unholy ; but such as are agreeable to the word of God. 2. They must not be superstitious such as may easily lead men astray, so as to attach to them worship, merit, or necessity, and which may occasion offence when observed. 3. They must not be too numerous, so as to be oppressive and burdensome. 4. They must not be empty, insignificant, and unprofitable; but tend to edification

It is clear that not all ceremonies need divine right, and that they can be changed by the church as necessary. This places them in the category of adiaphora and puts the Heidelberg’s teaching on liturgical ceremonies in the same broad category as the Lutheran and Anglican positions, in clear contrast with the later “Regulative Principle of Worship.”