2 But now to the present case let us come, if you please. For the voice is that sweet voice, so well known to the ears of the Church, the voice of our Lord Jesus Christ, and the voice of His Body, the voice of the Church toiling, sojourning upon earth, living amid the perils of men speaking evil and of men flattering. You will not fear a threatener, if you love not a flatterer. He therefore, of whom this is the voice, has observed and has seen, that all men speak justice.
For what man does dare not to speak it, lest he be called unjust? When, therefore, as though he were hearing the voices of all men, and were observing the lips of all men, he cried out to them, “If truly indeed justice ye speak,”— if not falsely justice ye speak, if not one thing on lips does sound, while another thing is concealed in hearts—“judge right things, you sons of men.” Hear out of the Gospel His own voice, the very same as is in this Psalm: “Hypocrites,” says the Lord to the Pharisees, “how are you able good things to speak, when you are evil men?....Either make the tree good, and the fruit thereof good: or make the tree evil, and the fruit thereof evil.” Why will you whiten you, wall of mud?
I know your inward parts, I am not deceived by your covering: I know what you hold forth, I know what you cover. “For there was no need for Him, that any one to Him should bear testimony of man: for He knew Himself what was in man.” For He knew what was in man, who had made man, and who had been made Man, in order that He might seek man....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)