8 This Psalm therefore concludes to this purpose: “O Israel, trust in the Lord, from this time forth and even unto eternity”. But the word seculum does not always mean this world, but sometimes eternity; since eternity is understood in two ways; until eternity, that is, either evermore without end, or until we arrive at eternity. How then is it to be understood here? Until we arrive at eternity, let us trust in the Lord God; because when we have reached eternity, there will be no longer hope, but the thing itself will be ours.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)