6 This is a great mystery in the great Gospel of John; and to commend it the more forcibly to our attention, the last chapter has been made its place of record. Accordingly, inasmuch as there were seven disciples taking part in that fishing, Peter, and Thomas, and Nathaneal, and the two sons of Zebedee, and two others whose names are withheld, they point, by their septenary number, to the end of time. For there is a revolution of all time in seven days. To this also pertains the statement, that when the morning had come, Jesus stood on the shore; for the shore likewise is the limit of the sea, and signifies therefore the end of the world. The same end of the world is shown also by the act of Peter, in drawing the net to land, that is, to the shore. Which the Lord has Himself elucidated, when in a certain other place He drew His similitude from a fishing net let down into the sea: “And they drew it,” He said, “to the shore.” And in explanation of what that shore was, He added, “So will it be in the end of the world.”
Source: Tractates on the Gospel of John (New Advent)