When the Reformers and the post-Reformed referred to the “sufficiency of the Scriptures,” they specifically meant the adequacy of the Scriptures to communicate saving knowledge, to guide the Christian’s living, and to instruct the church in worship.
Throughout the biblical narrative, God always told His people how to conduct worship. There is never an example, in either the Old or New Testaments, where God’s people structure worship according to what the Scriptures do not say, but rather what they do say. An argument from silence is never exemplified as a means to determine what worship should and should not be.
The 2LBC reads:
The whole counsel of God concerning all things necessary for his own glory, man’s salvation, faith and life, is either expressly set down or necessarily contained in the Holy Scripture: unto which nothing at any time is to be added, whether by new revelation of the Spirit, or traditions of men. Nevertheless, we acknowledge the inward illumination of the Spirit of God to be necessary for the saving understanding of such things as are revealed in the Word, and that there are some circumstances concerning the worship of God, and government of the church, common to human actions and societies, which are to be ordered by the light of nature and Christian prudence, according to the general rules of the Word, which are always to be observed.(2LBC, 1.6)
Everything we need to know for our worship, or, one could say, for the living out of the Christian life, is communicated in the Scriptures. The first paragraph of the same chapter begins, “The Holy Scripture is the only sufficient, certain, and infallible rule of all saving knowledge, faith, and obedience.” The Scriptures do not leave the church an excuse for ignorance when it comes to personal living and how worship ought to be conducted.
Now, if the Scriptures are sufficient for our worship, if they are adequate in communicating to God’s people how God has commanded them to worship, adding unnecessary practices should be seen as a contradiction to the doctrine of biblical sufficiency.
Adding to worship is no better than adding to the law, for example. It is to say, most basically, that Scripture is not enough. There must, it’s commonly thought, be something else we need to do in order to be more “attractional,” or “evangelistic,” or [insert any made-up vision]. The presupposition behind such thought is identical to the Pharisaical reasoning in adding to the law of God. The Pharisees invented a goal and added the extra-Scriptural qualifications needed to accomplish that artificial goal.
An example of my claim is found in John 5:39. The Pharisees had a goal to keep the letter of the law apart from the spirit of the law. The passed over the riches of Christ in their zeal for a superficial and outward piety. In many evangelical churches, Christ is being passed over for the goal of numerical growth, entertainment, etc.
May Spirit humble our hearts, that we may desire Christ more and more each day.