Mark 6:47

(ubi sup.) The disciples indeed, who were still carnal, were amazed at the greatness of His virtue, they could not yet however recognise in Him the truth of the Divine Majesty. Wherefore it goes on, For their hearts were hardened. But mystically, the toil of the disciples in rowing, and the contrary wind, mark out the labours of the Holy Church, who amidst the beating waves of the world, and the blasts of unclean spirits, strives to reach the repose of her celestial country. And well is it said that the ship was in the midst of the sea, and He alone on land, for sometimes the Church is afflicted by a pressure from the Gentiles so overwhelming, that her Redeemer seems to have entirely deserted her. But the Lord sees His own, toiling on the sea, for, lest they faint in tribulations, He strengthens them by the look of His love, and sometimes frees them by a visible assistance. Further, in the fourth watch He came to them as daylight approached, for when man lifts up his mind to the light of guidance from on high, the Lord will be with him, and the dangers of temptations will be laid asleep.

Now the Lord permitted His disciples to be in danger, that they might learn patience; wherefore He did not immediately come to their aid, but allowed them to remain in danger all night, that He might teach them to wait patiently, and not to hope at once for help in tribulations. For there follows, And he saw them toiling in rowing, for the wind was contrary unto them: and about the fourth watch of the night, he cometh unto them walking upon the sea.