For God is the King of all the earth - He has shown himself to be a universal sovereign. All nations are subject to him, and he has a claim to universal praise.
Sing ye praises with understanding - Margin, Every one “that hath understanding.” Neither the text here, however, nor the margin, expresses the true idea of the original. The Hebrew is, “Sing a Maschil” - משׂכיל maśkı̂yl; that is, Sing, or play, a didactic psalm or tune; that is, a song or ode adapted to convey valuable lessons of instruction. See the word explained in the notes at the title to Psalms 32:1-11. The idea is, that the occasion was one on which “such” a psalm or song would be especially appropriate; an occasion on which great lessons or truths had been taught by the dealings of God, which it became his people now to set forth in a becoming manner. Those lessons or truths pertained to the fact that God is the great King over all the earth, or that he is a sovereign among the nations: a truth of immense importance to mankind, and a truth which the occasion on which the psalm was composed was especially adapted to bring to view.