2 The title then of it is, “On the end: a Psalm for understanding for the sons of Korah.” We have met with the sons of Korah in other titles of Psalms: and remember to have discussed and stated already the meaning of this name. Yet we must even now take notice of this title in such a way, that what we have said already should be no prejudice against our saying it again: for all were not present in every place where we said it. Now Korah may have been, as indeed he was, a certain definite person; and have had sons, who might be called “the sons of Korah;” let us however search for the secret of which this is the sacrament, that this name may bring to light the mystery with which it is pregnant.
For there is some great mystery in the matter that the name “sons of Korah” is given to Christians. Why “sons of Korah”? They are “sons of the bridegroom, sons of Christ.” Why then does “Korah” stand for Christ? Because “Korah” is equivalent to “Calvaria.”...Therefore, the “sons of the bridegroom,” the sons of His Passion, the sons redeemed by His Blood, the sons of His Cross, who bear on their forehead that which His enemies erected on Calvary, are called “the sons of Korah;” to them is this Psalm sung as a Psalm for “understanding.”
Let then our understanding be roused: and if the Psalm be sung to us, let us follow it with our “understanding.”...Run to the brooks; long after the water-brooks. “With God is the fountain of Life;” a “fountain” that shall never be dried up: in His “Light” is a Light that shall never be darkened. Long thou for this light: for a certain fountain, a certain light, such as your bodily eyes know not; a light to see which the inward eye must be prepared; a fountain, to drink of which the inward thirst is to be kindled.
Run to the fountain; long for the fountain; but do it not anyhow, be not satisfied with running like any ordinary animal; run thou “like the hart.” What is meant by “like the hart”? Let there be no sloth in your running; run with all your might: long for the fountain with all your might. For we find in “the hart” an emblem of swiftness.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)