13 For not because I have fallen, have You grown old: for You are strong to set me free, who hast been strong to humble me. “But You, O Lord, endurest for ever: and Your remembrance throughout all generations”. “Your remembrance,” because Thou dost not forget: “throughout all generations,” forasmuch as we know the promise of life, both present and future.
14. “You shall arise, and have mercy upon Sion: for it is time that Thou have mercy upon her”. What time? “But when the fullness of time had come, God sent forth His Son, made of a woman, made under the Law.” And where is Sion? “To redeem them that were under the Law.” First then were the Jews: for thence were the Apostles, thence those more than five hundred brethren, thence that later multitude, who had but one heart and one soul toward God. Therefore, “the time has come.” What time? “Behold, now is the accepted time: behold, now is the day of salvation.” Who says this? That Servant of God, that Builder, who said, “You are God's building.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)