John Calvin Commentary Psalms 68:3

"But let the righteous be glad; let them exult before God: Yea, let them rejoice with gladness." — Psalms 68:3 (ASV)

But the righteous shall be glad. It is here intimated by David that when God shows himself formidable to the wicked, this is with the intention of securing the deliverance of his Church. He would seem indirectly to contrast the joy of which he now speaks with the depression and grief felt by well-disposed men under the reign of Saul—suggesting that God follows a season of temporary trouble with returns of comfort, to prevent his people from being overwhelmed by despondency.

He also leaves us to infer that one reason for the joy they experience is derived from knowing that God is propitious to them and interests himself in their safety. The Hebrew words, מפני, mipne, and לפני, liphne, can have the same meaning; but I think that the Psalmist intended to note a distinction.

The wicked flee from the presence of God, because it inspires them with terror; the righteous, in contrast, rejoice in it, because nothing delights them more than to think that God is near them. When commenting on the passage Psalm 18:26, we saw why the Divine presence terrifies some and comforts others: for with the pure he will show himself pure, and with the froward he will show himself froward. One expression is heaped by the Psalmist upon another to show how great the joy of the Lord’s people is, and how entirely it possesses and occupies their affections.