2 “And Jesus comes, and takes bread, and gives them, and fish likewise.” We are likewise told here, you see, on what they dined; and of this dinner we also will say something that is sweet and salutary, if we, too, are made by Him to partake of the food. It is related above that these disciples, when they came to the land, “saw a fire of coals laid, and a fish laid thereon, and bread.” Here we are not to understand that the bread also was laid upon the coals, but only to supply, They saw.
And if we repeat this verb in the place where it ought to be supplied, the whole may read thus: They saw coals laid, and fish laid thereon, and they saw bread. Or rather in this way: They saw coals laid, and fish laid thereon; they saw also bread. At the Lord's command they likewise brought of the fishes which they themselves had caught; and although their doing so might not be actually stated by the historian, yet there has been no silence in regard to the Lord's command. For He says, “Bring of the fishes which you have now caught.”
And when we have such certainty that He gave the order, will any suppose that they failed to obey it? Of this, therefore, the Lord prepared the dinner for these His seven disciples, namely, of the fish which they had seen laid upon the coals, with an addition thereto from those which they had caught, and of the bread which we are told with equal distinctness that they had seen. The fish roasted is Christ having suffered; He Himself also is the bread that comes down from heaven. With Him is incorporated the Church, in order to the participation in everlasting blessedness.
For this reason is it said, “Bring of the fish which you have now caught,” that all of us who cherish this hope may know that we ourselves, through that septenary number of disciples whereby our universal community may in this passage be understood as symbolized, partake in this great sacrament, and are associated in the same blessedness. This is the Lord's dinner with His own disciples, and herewith John, although having much besides that he might say of Christ, brings his Gospel, with profound thought and an eye to important lessons, to a close.
For here the Church, such as it will be hereafter among the good alone, is signified by the draught of an hundred and fifty-three fishes; and to those who so believe, and hope, and love, there is demonstrated by this dinner their participation in such super-eminent blessedness.
Source: Tractates on the Gospel of John (New Advent)