1 With this third manifestation of Himself by the Lord to His disciples after His resurrection, the Gospel of the blessed Apostle John is brought to a close, of which we have already lectured through the earlier part as we were able, on to the place where it is related that an hundred and fifty-three fishes were taken by the disciples to whom He showed Himself, and for all they were so large, yet were not the nets broken. What follows we have now to take into consideration, and to discuss as the Lord enables us, and as the various points may appear to demand.
When the fishing was over, “Jesus says unto them, Come [and] dine. And none of those who sat down dared to ask Him, Who are You? knowing that it was the Lord.” If, then, they knew, what need was there to ask? And if there was no need, wherefore is it said, “they dared not,” as if there were need, but, from some fear or other, they dared not? The meaning here, therefore, is: so great was the evidence of the truth that Jesus Himself had appeared to these disciples, that not one of them dared not merely to deny, but even to doubt it; for had any of them doubted it, he ought certainly to have asked. In this sense, therefore, it was said, “No one dared to ask Him, Who are You?” as if it were, No one dared to doubt that it was He Himself.
Source: Tractates on the Gospel of John (New Advent)