1 It is called, “A Psalm, to the end, for the sons of Korah, for things secret.” Secret is it then; but He Himself, who in the place of Calvary was crucified, you know, has rent the veil, that the secrets of the temple might be discovered. Furthermore since the Cross of our Lord was a key, whereby things closed might be opened; let us trust that He will be with us, that these secrets may be revealed. What is said, “To the end,” always ought to be understood of Christ. For “Christ is the end of the law for righteousness to every one that believes.” But The End He is called, not because He consumes, but because He perfects. For ended call we the food which is eaten, and ended the coat which is woven, the former to consumption, the latter to perfection. Because then we have not where to go farther when we have come to Christ, Himself is called the end of our course. Nor ought we to think, that when we have come to Him, we ought to strive any further to come also to the Father. For this thought Philip also, when he said to Him, “Lord, show us the Father, and it suffices us.” When he said, “It suffices us,” he sought the end of satisfaction and perfection. Then said He, “Have I been so long time with you, and have you not known Me, Philip: he that has seen Me, has seen the Father.” In Him then have we the Father, because He is in the Father, and the Father in Him, and He and His Father are One.
2. “Our God is a refuge and strength”. There are some refuges wherein is no strength, whereto when any flees, he is more weakened than strengthened. Thou fleest, for example, to some one greater in the world, that you may make yourself a powerful friend; this seems to you a refuge. Yet so great are this world's uncertainties, and so frequent grow the ruins of the powerful day by day, that when to such refuge you have come, you begin to fear more than ever therein....Our refuge is not such, but our refuge is strength. When there we have fled, we shall be firm.
3. “A helper in tribulations, which find us out too much.” Tribulations are many, and in every tribulation unto God must we flee; whether it be a tribulation in our estate, or in our body's health, or about the peril of those dearest to us, or any other thing necessary to the sustaining of this life, refuge ought there to be none at all to a Christian man, other than his Saviour, other than his God, to whom when he has fled, he is strong. For he will not in himself be strong, nor will he to himself be strength, but He will be his strength, who has become his refuge. But, dearly beloved, among all tribulations of the human soul is no greater tribulation than the consciousness of sin. For if there be no wound herein, and that be sound within man which is called conscience, wherever else he may suffer tribulation, there will he flee, and there find God....You see, dearly beloved, when trees are cut down and proved by the carpenters, sometimes in the surface they seem as though injured and rotten; but the carpenter looks into the inner marrow as it were of the tree, and if within he find the wood sound, he promises that it will last in a building; nor will he be very anxious about the injured surface, when that which is within he declares sound. Furthermore, to man anything more inward than conscience is not found; what then profits it, if what is without is sound, and the marrow of conscience has become rotton? These are close and vehement overmuch, and as this Psalm says, too great tribulations; yet even in these the Lord has become a helper by forgiving sin. For the consciences of the ungodly hates nothing save indulgence; for if one says he has great tribulations, being a confessed debtor to the treasury, when he beholds the narrowness of his estate, and sees that he cannot be solvent; if on account of the distrainers every year hanging over him, he says that he suffers great tribulations, and does not breathe freely except in hope of indulgence, and that in things earthly; how much more the debtor of penalties out of the abundance of sins: when shall he pay what he owes out of his evil conscience, when if he pay, he perishes? For to pay this debt, is to undergo the penalties. Remains then that of His indulgence, we may be secure, yet so that, indulgence received, we return not again to contract debts....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)