The Regulative Principle is a term used to describe how God and the Bible order public worship. This is espoused by various Christian denominations (including hyper-Calvinists and Anabaptists). In layman’s terms, we can say the regulative principle, at its conservative extreme, says that Christians should not sing anything other than the Psalms in church (with a few exceptions in some groups), should not use instruments because there is no clear use of instruments in the New Testament church, and should not dance at all.
I wonder if they ever studied David’s worship style.
And David and all the house of Israel were making merry before the LORD, with songs and lyres and harps and tambourines and castanets and cymbals…And David danced before the LORD with all his might.
– 1 Samuel 6:5, 14
I will sing a new song to you, O God; upon a ten-stringed harp I will play to you.
– Psalm 144:9