Theophylact of Ohrid

But observe the disciples, how they are distinguished by their love for mankind! Taking pity on the people, they approach Christ and begin to entreat Him on their behalf. The Lord, however, testing and trying them to see whether they had recognized His power—that He could feed the people—says, "You give them something to eat." To this the disciples, as if in reproach, point out to Him, on the one hand, the greatness of their own poverty, and on the other, the multitude of the people, as though He did not know this. …

Commentary on Mark ↗

Theodoret of Cyrus

This incarnation was effected, not in seeming and unreality, but in reality. He did not only pass through the Virgin, as through a channel, but was verily made flesh of her. Like us He really ate, and of the Virgin was really suckled. For if the incarnation was an unreality, then our salvation is a delusion. The Christ was twofold—the visible man, the invisible God. He ate as man, verily like ourselves, for the flesh that He wore was of like passions with us; He fed the five thousand with five loaves as God. As man He really died. …

Dialogues 2 ↗

Augustine of Hippo

This in the Gospel of John is the answer of Philip, but Mark gives it as the answer of the disciples, wishing it to be understood that Philip made this answer as a mouthpiece of the others; although he might put the plural number for the singular, as is usual.

Catena Aurea by Aquinas ↗

Bede

And he answering said to them: Give them something to eat. He provokes the apostles to the breaking of the bread, so that by their testifying they have nothing, the greatness of the sign might be better known: at the same time insinuating that daily through them our fasting hearts must be fed, clearly when we are roused to love heavenly things either by their examples or their writings. …

On the Gospel of Mark ↗