1 Of this Psalm the title is: “At the end, in hymns, understanding to David himself.” What the “end” is, we will briefly call to your recollection, because you have known it. “For the end of the Law is Christ, for righteousness unto every man believing.” Be the attention therefore directed unto the End, directed unto Christ. Wherefore is He called the end? Because whatever we do, to Him we refer it, and when to Him we shall have come home, more to ask we shall not have. For there is an end spoken of which does consume, there is an end spoken of which does make perfect. In one sense, for instance, we understand it, when we hear, there is ended the food which was in eating; and in another sense we understand it when we hear, there is ended the vesture which was in weaving: in each case we hear, there is ended; but the food so that it no longer is, the vesture so that it is perfected. Our end therefore ought to be our perfection, our perfection Christ. For in Him we are made perfect, because of Himself the Head, the Members are we. And he has been spoken of as “the End of the Law,” because without Him no one does make perfect the Law. When therefore ye hear in the Psalms, “At the end,”— for many Psalms are thus superscribed,— be not your thought upon consuming, but upon consummation.
2. “In hymns:” in praises. For whether we are troubled and are straitened, or whether we rejoice and exult, He is to be praised, who both in tribulations does instruct, and in gladness does comfort. For the praise of God from the heart and mouth of a Christian man ought not to depart; not that he may be praising in prosperity, and speaking evil in adversity; but after the manner that this Psalm does prescribe, “I will speak good of the Lord in every time, always the praise of Him is in my mouth.” Thou dost rejoice; acknowledge a Father indulging: you are troubled; acknowledge a Father chastening. Whether He indulge, or whether He chasten, He is instructing one for whom He is preparing an inheritance.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)