John Calvin on Worship

"Every addition to His word, especially in this matter, is a lie."

It must be regarded as a fixed principle, that all modes of worship devised by man are detestable. The Lord cannot forget himself, and it is long since he declared that nothing is so offensive to him as to be worshipped by human inventions.

The doctrine of the true worship of God is not to be sought from men, because the Lord has faithfully and fully taught us in what way he is to be worshipped. He has been pleased to prescribe in his Law what is lawful and right, and thus restrict men to a certain rule, lest any should allow themselves to devise a worship of their own. As God values obedience more than sacrifices, it ought to be sufficient for the rejection of any mode of worship, that it is not sanctioned by the command of God.

John Calvin (July 10, 1509 - May 27, 1564)

I know how difficult it is to persuade the world that God disapproves of all modes of worship not expressly sanctioned by His Word. The opposite persuasion which cleaves to them, being seated, as it were, in their very bones and marrow, is, that whatever they do has in itself a sufficient sanction, provided it exhibits some kind of zeal for the honor of God. But since God not only regards as fruitless, but also plainly abominates, whatever we undertake from zeal to His worship, if at variance with His command, what do we gain by a contrary course? The words of God are clear and distinct, “Obedience is better than sacrifice.” “In vain do they worship me, teaching for doctrines the commandments of men” (1 Sam. 15:22; Mat. 15:9). Every addition to His word, especially in this matter, is a lie. Mere “will worship” is vanity.

(From Institutes of the Christian Religion)