4 Now then, such security received, what say they? “Therefore will not we fear, when the earth shall be confounded”. Just before anxious, suddenly secure; out of too great tribulations set in great tranquillity. For in them Christ was sleeping, therefore were they tossed: Christ awoke (as but now we heard out of the Gospel), He commanded the winds, and they were still. Since Christ is in each man's heart by faith, it is signified to us, that his heart as a ship in this world's tempest is tossed, who forgets his faith: as though Christ sleeping it is tossed, but Christ awaking comes tranquillity. Nay, the Lord Himself, what said He? “Where is your faith?” Christ aroused, aroused up faith, that what had been done in the ship, might be done in their hearts. “A helper in tribulations, which found us out too much.” He caused that therein should be great tranquillity.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)