Let us now see what is meant by the due worship of God. Its chief foundation is to acknowledge Him to be, as He is, the only source of all virtue, justice, holiness, wisdom, truth, power, goodness, mercy, life, and salvation; in accordance with this, to ascribe and render to Him the glory of all that is good, to seek all things in Him alone, and in every want have recourse to Him alone. Hence arises prayer, hence praise and thanksgiving — these being attestations to the glory which we attribute to Him. This is that genuine sanctification of His name which He requires of us above all things. To this is united adoration, by which we manifest for Him the reverence due to his greatness and excellency, and to this ceremonies are subservient, as helps or instruments, in order that, in the performance of divine worship, the body may be exercised at the same time with the soul. Next after these comes self-abasement, when, renouncing the world and the flesh, we are transformed in the renewing of our mind, and living no longer to ourselves, submit to be ruled and actuated by Him. By this self-abasement we are trained to obedience and devotedness to his will, so that his fear reigns in our hearts, and regulates all the actions of our lives. That in these things consists the true and sincere worship which alone God approves, and in which alone He delights, is both taught by the Holy Spirit throughout the Scriptures and is also, antecedent to discussion, the obvious dictate of piety. Nor from the beginning was there any other method of worshipping God, the only difference being, that this spiritual truth, which with us is naked and simple, was under the former dispensation wrapt up in figures. And this is the meaning of our Savior’s words, “The hour cometh, and now is, when the true worshippers shall worship the Father in spirit and in truth,” (John 4:23.)

For by these words he meant not to declare that God was not worshipped by the fathers in this spiritual manner, but only to point out a distinction in the external form, viz., That while they had the Spirit shadowed forth by many figures, we have it in simplicity. But it has always been an acknowledged point, that God, who is a Spirit, must be worshipped in spirit and in truth.

Moreover, the rule which distinguishes between pure and vitiated worship is of universal application, in order that we may not adopt any device which seems fit to ourselves, but look to the injunction of Him who alone is entitled to prescribe. Therefore, if we would have Him to approve our worship, this rule, which he everywhere enforces with the utmost strictness, must be carefully observed. For there is a twofold reason why the Lord, in condemning and prohibiting all fictitious worship, requires us to give obedience only to his own voice. First, it tends greatly to establish His authority that we do not follow our own pleasures but depend entirely on his sovereignty; and, secondly, such is our folly, that when we are left at liberty, all we are able to do is to go astray. And then when once we have turned aside from the right path, there is no end to our wanderings, until we get buried under a multitude of superstitions. Justly, therefore, does the Lord, in order to assert his full right of dominion, strictly enjoin what he wishes us to do, and at once reject all human devices which are at variance with his command. Justly, too, does he, in express terms, define our limits that we may not, by fabricating perverse modes of worship, provoke His anger against us.

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 Samuel 15:22; Matthew 15:9.)

Every addition to His word, especially in this matter, is a lie. Mere “will worship” ἐθελοθρησκία, a is vanity. This is the decision, and when once the judge has decided, it is no longer time to debate.

—John Calvin, The Necessity of Reforming the Church (1543)