3 “Day unto day utters word”. To the spiritual the Spirit gives out the fullness of the unchangeable Wisdom of God, the Word which in the beginning is God with God. “And night unto night announces knowledge.” And to the fleshly, as to those afar off, the mortality of the flesh, by conveying faith, announces future knowledge.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)