3 The meaning of the proper name, according to the exact sense of the Hebrew, affords us no small assistance in interpreting the passage. Ziphims mean what we call sprinklings of the face; these were called in Hebrew Ziphims. Now, by the Law, sprinkling was a cleansing from sins; it purified the people through faith by the sprinkling of blood, of which this same blessed David thus speaks: You shall sprinkle me with hyssop and I shall be cleansed; the Law, through faith, providing as a temporary substitute, in the blood of whole burnt-offerings, a type of the sprinkling with the blood of the Lord, which was to be. But this people, like the people of the Ziphims, being sprinkled on their face and not in their faith, and receiving the cleansing drops on their lips and not in their hearts, turned faithless and traitors towards their David, as God had foretold by the Prophet: This people honours Me with their lips, but their heart is far from Me. They were ready to betray David because, the faith of their heart being dead, they had performed all the mystical ceremonies of the Law with deceitful face.
Source: Homilies on the Psalms (New Advent)