John Calvin Commentary Psalms 81:1

"Sing aloud unto God our strength: Make a joyful noise unto the God of Jacob." — Psalms 81:1 (ASV)

Sing joyfully to God our strength. This psalm, it is probable, was appointed to be sung on the festival days when the Jews kept their solemn assemblies. In the introduction, the order of worship which God had commanded is set forth. They were not to stand deaf and dumb at the tabernacle, for the service of God does not consist in indolence, nor in cold and empty ceremonies; rather, by such practices as are prescribed here, they were to cherish among themselves the unity of faith, make an open profession of their piety, stir themselves up to continual progress in it, endeavor to join with one accord in praising God, and, in short, continue steadfast in the sacred covenant by which God had adopted them to Himself.

Since this was the use of festival days under the Law, we may conclude that whenever true believers assemble today, the purpose they ought to have in view is to engage in the practices of religion: to call to their remembrance the benefits they have received from God, to make progress in the knowledge of His word, and to testify to the oneness of their faith.

People only mock God by presenting Him with vain and unprofitable ceremonies, unless the doctrine of faith goes before, stirring them up to call upon God, and unless the remembrance of His benefits also provides material for praise. Indeed, it is rather a profanation of His name when people quench the light of divine truth and satisfy themselves with performing mere outward service.

Accordingly, the faithful are not only commanded here to come together to the tabernacle, but are also taught the purpose for which they are to assemble there: that the free and gracious covenant God has made with them may be brought anew to their remembrance to increase their faith and piety, and that, as a result, the benefits they have received from Him may be celebrated and their hearts thereby moved to thanksgiving.

With respect to the tabret, harp, and psaltery, we have observed before, and will find it necessary to repeat the same remark later, that the Levites, under the Law, were justified in using instrumental music in the worship of God. This was because it was His will to train His people by such rudiments while they were still tender and like children, until the coming of Christ.

But now that the clear light of the gospel has dissipated the shadows of the Law and taught us that God is to be served in a simpler form, it would be foolish and mistaken to imitate what the prophet commanded only for those of his own time.

From this, it is apparent that Roman Catholics have shown themselves to be like apes in applying this to themselves.

Under the term new moon, by synecdoche, all the other high feasts are included. Sacrifices were offered daily; but the days on which the faithful met together at the tabernacle, according to the express appointment of the Law, are pre-eminently called the days of sacrifice.