In its basic form, the regulative principle of worship states that we are only to worship God as he has commanded, not adding or taking away from Scripture. It was some years ago, while I was still in university, that I became convinced that this regulative principle of worship is the Reformed, confessional, position on worship. It was not difficult to see that the teaching of Heidelberg Catechism QA 96 (we are not to worship God “in any other manner than he has commanded in his Word”) is biblical and exactly in line with other Reformed confessions like the Westminster Standards. I also came to see that this Reformed principle of worship was not only in the Belgic Confession in article 32, but also in article 7. I wrote a paper on that, demonstrating that the regulative principle, according to our confession, is simply the liturgical outworking of Sola Scriptura. I have also argued that denying the regulative principle of worship has serious consequences and leads to bizarre liturgical innovations.
The principle itself is straightforward. Application of the principle is where we often encounter differences. It took some time for me to work through some of these issues too. For example, there was a time when I struggled with understanding how one could celebrate the birth of Christ on December 25 and still hold to the regulative principle. However, through further research and conversations with others, I came to peace with that. I still hold to the regulative principle, but I can also in good conscience join with God’s people in commemorating the birth of our Saviour on December 25. Rather than have me explain in detail how I have reconciled these things, I highly recommend this article by my colleague Daniel Hyde. This article is being published in the 2015 issue of the Mid-America Journal of Theology. It helpfully explains how one can both hold to the regulative principle and worship on the “feast days” or “days of commemoration.”