In Reformed churches, there is a precept referred to as "the Regulative Principle of Worship" (hereafter, RPW). According to this principle, nothing is permitted in worship except that which is commanded in Scripture, or may be inferred from it. This contrasts with Lutheranism, which holds that all is permitted, except what is forbidden, and with Catholicism, which seems to have no principle of worship except the limits of papal imagination.
In the Directory for the Public Worship of God, adopted by the Church of Scotland with the Westminster Standards in the XVIIth Century, we read in the preface, "our care hath been to hold forth such things as are of divine institution in every ordinance; and other things we have endeavoured to set forth according to the rules of Christian prudence, agreeable to the general rules of the word of God."
The biblical basis for the RPW is primarily found in the IInd Commandment (Ex. 20:4-6, Deut. 5: 8-10): "You shall not make for yourself a carved image, or any likeness of anything that is in heaven above, or that is in the earth beneath, or that is in the water under the earth." While the commandment is narrowly tailored, addressing merely the use of images in worship, its application is broadened in the historical portions of the Old Testament.
In the story of Jeroboam, the first king of Israel after the dividing of the Davidic kingdom, we find two occasions of will-worship, i. e., worship after the desires of man, rather than the commandment of God.
In I Kings 12:33, Jeroboam goes "up to the altar that he had made in Bethel on the fifteenth day in the eighth month, in the month that he had devised from his own heart. And he instituted a feast for the people of Israel and went up to the altar to make offerings." Here, we see Jeroboam violate biblical worship in three ways: he changed the calendar of biblical feasts, to the point of creating a new month; he built an altar for worship away from the Temple in Israel; and he performed a rite which was properly for the levitical priests (compare Saul's similar sin in I Samuel 13:8-23).
Again, in I Kings 13:33, we see Jeroboam appointing a new class of priests for the "high places" (places of pagan worship). In fact, his standard was so lax, that "any who would, he ordained." This is a violation of God's institution of the Aaronic priesthood (Exodus 29:44).
And what are the consequences of Jeroboam's actions? I Kings 13:34, "this thing became a sin to the house of Jeroboam, so as to cut it off and to destroy it from the face of the earth."
Just as no responsible parent would leave it to his children to make the rules for the household, God does not leave it to His creatures to determine how to worship Him. That concept seems to me to be so obvious, even without the biblical instructions, that I cannot conceive how professing Christians can so easily disregard it. I have written before (use the tags below) on even Presbyterian churches which have become hardly more than pagans in their worship. Just as with His judgment on Saul, surely God will rebuke such rebellion among His professing people.