John Calvin Commentary Psalms 119:172

"Let my tongue sing of thy word; For all thy commandments are righteousness." — Psalms 119:172 (ASV)

My tongue shall speak of thy word. Here the Psalmist says that when he has profited in God’s law, he will also apply himself to teaching it to others. This order is undoubtedly to be observed: divine truth must take root in our hearts before we engage in the work of teaching it to others.

Yet everyone, according to the measure of their faith, ought to communicate to their fellow believers what they have received, so that the doctrine, whose use and fruit God would have displayed for the common edification of the Church, may not be buried. Furthermore, the reason is given that ought to stir up all the godly to declare the law of God—namely, because by this means righteousness is spread throughout the whole world.

When the Prophet honors the commandments of God with the title of righteousness, he does not simply express his approval of them, but he indirectly shows that, until this rule holds sway in governing humankind, the whole world is one scene of sad and horrible confusion. Yet, let my readers judge whether the word answer or witness, which the Hebrew verb ענה, anah, properly signifies, is not more suitable in this place than speak; bringing out this sense—“My tongue shall bear witness or answer to thy word; because the true knowledge of righteousness is to be sought only in the word;” but in that case, it will be necessary to supply the letter ל, lamed, to the word אמרתך, imrathecha, so that it may read—to thy word.