11 For He that “did burst asunder the sea and made them go through, did confine the waters as it were in bottles”, in order that the water might stand up first as if it were shut in, is able by His grace to restrain the flowing and ebbing tides of carnal desires, when we renounce this world, so that all sins having been thoroughly washed away, as if they were enemies, the people of the faithful may be made to pass through by means of the Sacrament of Baptism. He that “led them home in the cloud of the day, and in the whole of the night in the illumination of fire”, is able also spiritually to direct goings if faith cries to Him, “Direct my goings after Your word.” Of Whom in another place is said, “For Himself shall make your courses right, and shall prolong your goings in peace” through Jesus Christ our Lord, whose Sacrament in this world, as it were in the day, is manifest in the flesh, as if in a cloud; but in the Judgment it will be manifest like as in a terror by night; for then there will be a great tribulation of the world like as it were fire, and it shall shine for the just and shall burn for the unjust. “He that burst asunder the rock in the desert, and gave them water as in a great deep”; “and brought out water from the rock, and brought down waters like rivers”, is surely able upon thirsty faith to pour the gift of the Holy Spirit (the which gift the performance of that thing did spiritually signify), to pour, I say, from the Spiritual Rock that followed, which is Christ: who stood and cried, “If any is thirsty, let him come to Me:” and, “he that shall have drunk of the water which I shall give, rivers of living water shall flow out of his bosom.” For this He spoke, as is read in the Gospel, to the Spirit, which they were to receive that believed in Him, unto whom like the rod drew near the wood of the Passion, in order that there might flow forth grace for believers.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)