8 Diapsalma. The answer of God: “I will give you understanding, and will set you in the way in which you shall go;” I will give you understanding after confession, that you depart not from the way in which you should go; lest you wish to be in your own power. “I will fix Mine Eyes upon you”; so will make sure upon you My Love.
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.
10. “Many are the scourges of the sinner:” much is he scourged, who, confessing not his sins to God, would be his own ruler. “But he that trusts in the Lord, mercy compasses him about”; but he that trusts in the Lord, and submits himself to His rule, mercy shall compass him about.
11. “Be glad in the Lord, and rejoice, you righteous:” be glad, and rejoice, you righteous, not in yourselves, but in the Lord. “And glory, all you that are right in heart”: and glory in Him, all you who understand that it is right to be subject unto Him, that so ye may be placed above all things beside.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)