John Calvin on Isaiah 42:12

12. Let them give glory to Jehovah. He explains what the nature of that shouting will be, that is, to celebrate the praises of God; for his goodness and mercy shall be everywhere seen; and therefore he enjoins them to celebrate this redemption with a cheerful voice, because the blessed consequences of it shall be shared by all the nations. And thus we are reminded to cry aloud in the present day with the greatest earnestness when we proclaim the praises of God, that we ourselves may be inflamed, and may excite others by our example to act in the same manner; for to be lukewarm, or to mutter, or to sing, as the saying is, to themselves and to the muses, is impossible for those who have actually tasted the grace of God.