John Calvin Commentary Isaiah 42:10

"Sing unto Jehovah a new song, and his praise from the end of the earth; ye that go down to the sea, and all that is therein, the isles, and the inhabitants thereof." — Isaiah 42:10 (ASV)

Sing to Jehovah. He now exhorts the people to gratitude, for God’s favors ought always to excite us, by remembering them, to give thanks and to celebrate his praises. Besides, by that exhortation he calls believers to behold the prophecy as actually accomplished and confirms those promises of which he spoke. We ought to observe this as the Prophet's design: that there is no reason why believers, though severely oppressed, should give way to sorrow, but that good hope ought to encourage them to gladness, so that they may now prepare to give thanksgiving.

The subject of this song is that Christ has been revealed to the world and sent by the Father to relieve the miseries of his Church, and to restore her to perfect order, and indeed, as it were, to renew the whole world. As this was difficult to believe, the Prophet wished to remove every doubt, in order to embed these predictions more deeply in their hearts. Nor ought we to wonder that the Prophet labors so hard to arouse them when they were reduced to the greatest difficulties and had no longer any hope of safety. The mere aspect of things might shake their faith and even produce suspicion that all that the prophets had foretold was unfounded and absurd. The purpose of this exhortation, therefore, is that when affairs are utterly desperate, they should be cheerful and rely on these promises.

A new song. By new he means an excellent, beautiful, and elegant song, not one that is ordinary or common, but a song that may arouse people to admiration, as it relates to the extraordinary grace of God, of which there had never been so remarkable an example. In this sense, it is also used in Psalm 33:3 and Psalm 96:1. New is here contrasted with what is Ordinary, and thus he extols the infinite mercy of God, which was to be revealed in Christ, and which ought therefore to be celebrated and sung with the highest praises.

Hence we infer that each of us ought to be more zealous in proclaiming the praises of God, in proportion to the greater number of favors we have received. It is indeed the duty of all people to sing praise to God, for there is no person who is not bound to it by the strongest obligations; but more lofty praises ought to proceed from those on whom more valuable gifts have been bestowed. Now, since God has opened the fountain of all blessings in Christ and has displayed all spiritual riches, we need not wonder if he demands that we offer to him an extraordinary and excellent sacrifice of praise.

It ought to be observed that this song can only be sung by renewed people, for it ought to proceed from the deepest feeling of the heart, and therefore we need the direction and influence of the Spirit, so that we may sing these praises in a proper manner. Besides, he does not exhort one or a few nations to do this, but all the nations in the world, for Christ was sent to all of them.