8 “Be not therefore lifted up: speak not iniquity against God”....What says He in another Psalm? “These things you have done,” having enumerated certain sins. “These things you have done,” He says, “and was silent.” What is, “I was silent”? He is never silent with commandment, but meanwhile He is silent with punishment: He is keeping still from vengeance, He does not pronounce sentence against the condemned. But this man says thus, I have done such and such things, and God has not taken vengeance; behold I am whole, nought of ill has befallen me.
“These things you have done, and I was silent: you have suspected iniquity, that I shall be like you.” What is, “that I shall be like you”? Because you are unjust, even Me you have deemed unjust; as though an approver of your misdeeds, and no adversary, no avenger thereof. And what afterwards says He to you? “I will convict you, and will set you before your own face”? What is this? Because now by sinning behind your back you set yourself, see not yourself, examinest not yourself; I will set you before yourself, and will bring upon you punishment from yourself.
So also here, “Speak not iniquity against God.” Attend. Many men speak this iniquity; but dare not openly, lest as blasphemers they be abhorred by godly men: in their heart they gnaw upon these things, within they feed upon such impious food; it delights them to speak against God, and if they break not out with tongue, in heart they are not silent. Whence in another Psalm is said, “The fool has said in his heart, There is no God.” The fool has said, but he has feared men: he would not say it where men might hear; and he said it in that place where He might Himself hear concerning whom he said it.
Therefore here also in this Psalm (dearly beloved attend), whereas that which He said, “Do not speak iniquity against God,” this He saw many men do in heart, He has also added, “for neither from East, nor from West, nor from the deserts of the mountains, for God is Judge”. Of your iniquities God is Judge. If God He is, everywhere He is present. Whither will you take yourself away from the eyes of God, so that in some quarter you may speak that which He may not hear? If from the East God judges, withdraw into the West, and say what you will against God: if from the West, go into the East, and there speak: if from the deserts of the mountains He judges, go into the midst of the peoples, where you may murmur to yourself.
From no place judges He that everywhere is secret, everywhere open; whom it is allowed no one to know as He is, and whom no one is permitted not to know. Take heed what you doest. You are speaking iniquity against God. “The Spirit of the Lord has filled the round world” (another Scripture says this), “and that which contains all things has knowledge of the voice: wherefore he that speaks unjust things cannot be hid.” Do not therefore think God to be in places: He is with you such an one as you shall have been.
What is such an one as you shall have been? Good, if you shall have been good; and evil to you He will seem, if evil you shall have been; but a Helper, if good you shall have been; an Avenger, if evil you shall have been. There you have a Judge in your secret place. Willing to do something of evil, from the public you retire into your house, where no enemy may see; from those places of your house which are open and before the eyes of men, you remove yourself into a chamber; you fear even in your chamber some witness from some other quarter, you retire into your heart, there you meditate.
He is more inward than your heart. Whithersoever therefore you shall have fled, there He is. From yourself whither will you flee? Will you not follow yourself wherever you shall flee? But since there is One more inward even than yourself, there is no place whither you may flee from God angry, but to God reconciled. There is no place at all whither you may flee. Will you flee from Him? Flee to Him....What then shall we do now? “Let us come before His face,” ἐ ν ἐξομολογήσει, come before in confession: He shall come gentle whom you had made angry.
“Neither from the deserts of the mountains, for God is Judge:” not from the East, not from the West, not from the deserts of the mountains. Wherefore? “For God is Judge.” If in any place He were, He would not be God: but because God is Judge, not man, do not expect Him out of places. His place you will be, if you are good, if after having confessed you shall have invoked Him.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)