Is inditing. Heb. rachash, a word occurring only here in the OT. In post-Biblical Hebrew it means “to be actively astir.” Such a definition fits the present context. David is so stirred by the wonder and the beauty of his vision that he must give it expression. Soul-stirring preaching, like great poetry, comes from a soul that is stirred (see Matt. 12:34).
My tongue. David wishes his expression to be that of a rapid writer—warm, free, overflowing with emotion.
Pen. Heb. ‘eṭ, “stylus,” a writing instrument used for inscribing letters on stone (see Job 19:24).
This unusual formal introduction lends solemnity and importance to the theme of the poem.