John Calvin Commentary Psalms 66:4

"All the earth shall worship thee, And shall sing unto thee; They shall sing to thy name. Selah" — Psalms 66:4 (ASV)

All the earth shall worship you. The Psalmist had good reason for insisting on this one point again and again. Though all tongues were tuned to the praise of God, they never could adequately extol it; and yet such are the negligence and the perversity of men, that they will scarcely lift one feeble note in celebration of a theme which should command their united strength and might.

We have another prediction here, of a time to come when God would be worshipped, not only by the Jews, a small section of the human family, but by all the nations which would be eventually brought under his government.

And we are not to consider that he refers to such a worship as would be constrained, and only not withheld because resistance might be dangerous, but to the sincere homage of the heart—they shall sing to you! They shall sing to your name. Praise is the best of all sacrifices (as we are told in Psalm 50:14, 23) and the true evidence of godliness.