“It must be regarded as a fixed principle that all modes of worship devised by man are detestable.”
(Institutes, I.XI.4)

“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.”
(Institutes, IV.X.17)

“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.”
(Institutes, IV.X.B)

“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 device a worship of their own.”
(Institutes, I.XII.3)

“All worship of man’s device is repudiated by the Holy Spirit as degenerate.”
(Institutes I.V.3)

“…but 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.”
(“On the Necessity of Reforming the Church”, Selected Works of John Calvin, Grand Rapids: Baker, 1983, p.132)

“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. This is the decision, and when once the judge has decided, it is no longer time to debate.”
(“On the Necessity of Reforming the Church”, Selected Works of John Calvin, Grand Rapids: Baker, 1983,p. 128)

“We know that elsewhere there are many other ceremonies which we deny not to be very ancient, but because they have been invented at pleasure, or at least on grounds which, be these what they say, must be trivial, since they have been devised without authority from the word of God, and because, on the other hand, so many superstitions have sprung from them, we have felt no hesitation in abolishing them, in order that there might be nothing to prevent the people from going directly to Jesus Christ. First, whatever is not commanded, we are not free to choose. Secondly, nothing which does not tend to edification ought to be received into the Church. If anything of the kind has been introduced, it ought to be taken away, and by much stronger reason, whatever serves only to cause scandal, and is, as it were, an instrument of idolatry and false opinion, ought on no account to be tolerated.”
(“Form for Administering the Sacraments”, Calvin’s Selected Works, Grand Rapids: Baker, 1983, Vol.2, Tracts Part 2, pp.117,118)

“By forbidding the addition, or diminishing of anything, he plainly condemns as illegitimate whatever men invent of their own imagination; whence it follows that they, who in worshipping God are guided by any rule save that which He Himself has prescribed, make to themselves false gods; and, therefore, horrible vengeance is denounced by Him against those who are guilty of this temerity…”
(Commentary on Deuteronomy 12:32)

“But Christ has faithfully and accurately given the meaning, that in vain is God worshipped, when the will of men is substituted in the room of doctrine. By these words, all kinds of will-worship, (ethelothzeskeia,) as Paul calls it, (Colossians 2:23,) are plainly condemned. For, as we have said, since God chooses to be worshipped in no other way than according to his own appointment, he cannot endure new modes of worship to be devised. As soon as men allow themselves to wander beyond the limits of the Word of God, the more labor and anxiety they display in worshipping him, the heavier is the condemnation which they draw down upon themselves; for by such inventions religion is dishonored….for Christ declares them to be mistaken who bring forward, in the room of doctrine, the commandments of men, or who seek to obtain from them the rule for worshipping God. Let it therefore be held as a settled principle, that, since obedience is more highly esteemed by God than sacrifices, (1 Samuel 15:22,23,) all kinds of worship invented by men are of no estimation in his sight; nay more, that, as the prophet declares, they are accursed and detestable.”
(Commentary on Matthew 15:9)

I am a Reformed Presbyterian. I offer all content as my own personal reflections. I am not a licensed minister.