Luke 5:4

Now in a mystery, the ship of Peter, according to Matthew, is beaten about by the waves, (Matt. 8:24.) according to Luke, is filled with fishes, in order that you might understand the Church at first wavering, at last abounding. The ship is not shaken which holds Peter; that is which holds Judas. In each was Peter; but he who trusts in his own merits is disquieted by another's. Let us beware then of a traitor, lest through one we should many of us be tossed about. Trouble is found there where faith is weak, safety here where love is perfect. Lastly, though to others it is commanded, Let down your nets, to Peter alone it is said, Launch out into the deep, i. e. into deep researches. What is so deep, as the knowledge of the Son of God! But what are the nets of the Apostles which are ordered to be let down, but the interweaving of words and certain folds, as it were, of speech, and intricacies of argument, which never let those escape whom they have once caught. And rightly are nets the Apostolical instruments for fishing, which kill not the fish that are caught, but keep them safe, and bring up those that are tossing about in the waves from the depths below to the regions above. But he says, Master, we have toiled the whole night and have caught nothing; for this is not the work of human eloquence but the gift of divine calling. But they who had before caught nothing, at the word of the Lord inclosed a great multitude of fishes.

(Hom. 6. in Matt.) For in His condescension to men, He called the wise men by a star, the fishermen by their art of fishing.

Having sufficiently taught the people, He returns again to His mighty works, and by the employment of fishing fishes for His disciples. Hence it follows, When he had left off speaking, he said unto Simon, Launch out into the deep, and let down your nets for a draught.