10 What then does Peter's daring to come to Him on the waters also signify? For Peter generally stands for a figure of the Church. What else then do we think is meant by, “Lord, if it be Thou, bid me come unto You on the water;” but, Lord, if You are true, and in nothing speakest falsely, let Your Church also be glorified in this world, because prophecy has proclaimed this concerning You. Let her walk then on the waters, and so let her come to You, to whom it is said, “The rich among the people shall entreat Your favour.” But since to the Lord the praise of men is no temptation, but men are ofttimes in the Church disordered by human praises and honours, and well near sunk by them; therefore did Peter tremble in the sea, terrified at the great violence of the storm.
For who does not fear those words, “They who call you blessed cause you to err, and disturb the ways of your feet?” And because the soul has much wrestling against the eager desire of human praise, good is it in such peril to betake one's self to prayer and earnest entreaty: lest haply he who is charmed with praise, be overwhelmed and sunk by blame. Let Peter cry out as he totters in the water, and say, “Lord, save me.” For the Lord will reach forth His hand, and though He chide, saying, “O you of little faith, wherefore did you doubt?” wherefore did you not look straight forward upon Him to whom you were making your way, and glory only in the Lord?
Nevertheless He will snatch him from the waves, and will not suffer Him to perish, who confesses his own infirmity, and begs His help. But when they had received the Lord into the ship, and their faith was strengthened and all doubt removed, and the tempests of the sea assuaged, so that they had come to a firm and secure landing, they all worship Him, saying, “Of a truth You are the Son of God.” For this is that everlasting joy, where Truth made manifest, and the Word of God, and the Wisdom by which all things were made, and the exceeding height of His Mercy, are both known and loved.
Source: Sermons on Selected Lessons of the New Testament (New Advent)