12 Jesus saith to them: Come, and dine. And none of them who were at meat, durst ask him: Who art thou? knowing that it was the Lord.
Chrysostom: He ate however not to satisfy the wants of nature, but to show the reality of His resurrection.
Augustine: The bodies of the just, when they rise again, shall need neither the word of life that they die not of disease, or old age, nor any bodily nourishment to prevent hunger and thirst. For they shall be endowed with a sure and inviolable gift of immortality, that they shall not eat of necessity, but only be able to eat if they will. Not the power, but the need of eating and drinking shall be taken away from them; in like manner as our Savior after His resurrection took meat and drink with His disciples, with spiritual but still real flesh, not for the sake of nourishment, but in exercise of a power.
13 And Jesus cometh and taketh bread, and giveth them, and fish in like manner. 14 This is now the third time that Jesus was manifested to his disciples, after he was risen from the dead.
Augustine: Mystically, the fried fish is Christ Who suffered. And He is the bread that came down from heaven. To Him the Church is united to His body for participation of eternal bliss. Wherefore He says, Bring of the fishes which you have now caught ; to signify that all of us who have this hope, and are in that septenary number of disciples, which represents the universal Church here, partake of this great sacrament, and are admitted to this bliss.
Bede: He deigned to be hid in the waters of human nature, and to be taken in the net of our night; and having become a fish by the taking of humanity, became bread to refresh us by His divinity.
Gregory: By holding this last feast with seven disciples, he declares that they only who are full of the sevenfold grace of the Holy Spirit, shall be with Him in the eternal feast. Time also is reckoned by periods of seven days, and perfection is often designated by the number seven. They therefore feast upon the presence of the Truth in that last banquet, who now strive for perfection.
Scripture from the Douay-Rheims Bible. Commentary from St. Thomas Aquinas, Catena Aurea, Vol. IV (London: Rivington, 1845).