In Institutes 2.7.1, Calvin discusses why the Law was “superadded” at Sinai. The giving of the Law to Moses and, through him, to Israel can only be properly understood, he believes, when connected with the end of the Law, which was always Christ and the spiritual worship of God by a “kingdom of priests, and an holy nation.” This connection is most clearly seen in the ceremonies of the Law which, if separated from their substance in Christ, become, in Calvin’s view, “a mere mockery.”
From the whole course of the observations now made, we may infer, that the Law was not superadded about four hundred years after the death of Abraham in order that it might lead the chosen people away from Christ, but, on the contrary, to keep them in suspense until his advent; to inflame their desire, and confirm their expectation, that they might not become dispirited by the long delay. By the Law, I understand not only the Ten Commandments, which contain a complete rule of life, but the whole system of religion delivered by the hand of Moses. Moses was not appointed as a Lawgiver, to do away with the blessing promised to the race of Abraham; nay, we see that he is constantly reminding the Jews of the free covenant which had been made with their fathers, and of which they were heirs; as if he had been sent for the purpose of renewing it. This is most clearly manifested by the ceremonies. For what could be more vain or frivolous than for men to reconcile themselves to God, by offering him the foul odour produced by burning the fat of beasts? or to wipe away their own impurities by be sprinkling themselves with water or blood? In short, the whole legal worship (if considered by itself apart from the types and shadows of corresponding truth) is a mere mockery. Wherefore, both in Stephen’s address (Acts 7:44), and in the Epistle to the Hebrews, great weight is justly given to the passage in which God says to Moses, “Look that thou make them after the pattern which was showed thee in the mount,” (Exod. 25:40). Had there not been some spiritual end to which they were directed, the Jews, in the observance of them, would have deluded themselves as much as the Gentiles in their vanities. Profane men, who have never made religion their serious study, cannot bear without disgust to hear of such a multiplicity of rites. They not merely wonder why God fatigued his ancient people with such a mass of ceremonies, but they despise and ridicule them as childish toys. This they do, because they attend not to the end; from which, if the legal figures are separated, they cannot escape the charge of vanity. But the type shows that God did not enjoin sacrifice, in order that he might occupy his worshippers with earthly exercises, but rather that he might raise their minds to something higher. This is clear even from His own nature. Being a spirit, he is delighted only with spiritual worship. The same thing is testified by the many passages in which the Prophets accuse the Jews of stupidity, for imagining that mere sacrifices have any value in the sight of God. Did they by this mean to derogate in any respect from the Law? By no means; but as interpreters of its true meaning, they wished in this way to turn the attention of the people to the end which they ought to have had in view, but from which they generally wandered. From the grace offered to the Jews we may certainly infer, that the law was not a stranger to Christ. Moses declared the end of the adoption of the Israelites to be, that they should be “a kingdom of priests, and an holy nation,” (Exod. 19:6). This they could not attain, without a greater and more excellent atonement than the blood of beasts. For what could be less in accordance with reason, than that the sons of Adam who, from hereditary taint, are all born the slaves of sin, should be raised to royal dignity, and in this way made partakers of the glory of God, if the noble distinction were not derived from some other source? How, moreover, could the priestly office exist in vigour among those whose vices rendered them abominable in the sight of God, if they were not consecrated in a holy head? Wherefore, Peter elegantly transposes the words of Moses, teaching that the fulness of grace, of which the Jews had a foretaste under the Law, is exhibited in Christ, “Ye are a chosen generation, a royal priesthood,” (1 Pet. 2:9). The transposition of the words intimates that those to whom Christ has appeared in the Gospel, have obtained more than their fathers, inasmuch as they are all endued with priestly and royal honour, and can, therefore, trusting to their Mediator, appear with boldness in the presence of God.