19 “Let these things be written for those that come after”. When these words were written, they profited not so much those among whom they were written for they were written to prophesy the New Testament, among men who lived according to the Old Testament. But God had both given that Old Testament, and had settled in that land of promise His own people. But since “Your remembrance is from generation to generation,” belongs not to the ungodly, but to the righteous; “in our generation” belongs to the Old Testament; while “in the other generation” belongs to the New Testament; and since the New Testament announces this that was prophesied, “Let these things be written for those that come after: and the people which shall be created, shall praise the Lord.”
Not the people which is created, but “the people which shall be created.” What is clearer, my brethren? Here is prophesied that creation of which the Apostle says: “Therefore if any man be in Christ, he is a new creature; old things are passed away; behold, all things have become new.” “For he has looked down from His lofty sanctuary.” He has looked down from on high, that He might come unto the humble: from on high He has become humble, that He might exalt the humble....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)