9 “Be not ye like horse or mule, which have no understanding:” and therefore would govern themselves. But says the Prophet, “Hold in their jaws with bit and bridle.” Do Thou then, O God, unto them “that will not come near You”, what man does to horse and mule, that by scourges Thou make them to bear Your rule.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)