John Calvin Commentary Psalms 89:1

"I will sing of the lovingkindness of Jehovah for ever: With my mouth will I make known thy faithfulness to all generations." — Psalms 89:1 (ASV)

I will sing of the mercies of Jehovah for ever. It must be kept in mind, as I have just observed, that the Psalmist opens with the praises of God and with recalling the Divine covenant, to encourage the faithful to strengthen their faith against the formidable assaults of temptation.

If, when we begin to pray, some despairing thought comes to us at the very outset, we must forcibly and resolutely break through it, lest our hearts faint and utterly fail.

The prophet's purpose, therefore, was to fortify the minds of the godly at the very beginning with stable and substantial supports. He intended that, by relying on the Divine promise—which, to outward appearance, had almost fallen to the ground—and by repelling all the assaults of temptation that severely shook their faith, they might confidently hope for the re-establishment of the kingdom and persevere in praying for this blessing.

From the sad spectacle of the decay that had begun, which Ethan saw, if he had listened to the dictates of carnal reason, he might have thought that both he and the rest of God’s believing people were deceived; but he expresses his determination to celebrate the mercies of God, which at that time were hidden from his view.

And since it was not easy for him to grasp and acknowledge the merciful character of God—of whose severity he had actual experience—he uses the plural phrase the Mercies of God, so that by reflecting on the abundance and variety of the blessings of Divine grace, he might overcome this temptation.