Numbers 11:21

Six hundred thousand on foot. He was not concerned with counting in detail the remaining three thousand. R’ Moshe Hadarshan explains that only those who went out of Egypt, wept.

But Mosheh said, Six hundred thousand footmen are the people among whom I dwell, and Thou hast said, I will give them flesh to eat for a month of days!

'ויאמר משה: שש מאות אלף וגו, we need to understand Moses’ words in the same way as when he had told G’d that the people “could not ascend the mountain” in Exodus 19,23. Of course they could have, but it was forbidden which to Moses meant that “they could not.” ואכלו חודש ימים, and he was also concerned about G’d’s threat that the meat would become repulsive to the people. (verse 20) He asked that seeing that there were over 600.000 adult males plus numerous children and women, the livestock of the people could hardly be sufficient to sustain such an ambitious program? He was afraid that possibly G’d had in mind to kill many of the people so that it would be possible to feed the survivors on the meat of their herds and flocks so that G’d’s prediction would come true. Alternatively, G’d would have to perform miracles for these people to supply them with meat, something Moses felt that they had hardly deserved. [at any rate, Moses did not mean to imply doubt about G’d’s ability to make good on what He had said. Ed.]

שש מאות אלף רגלי, this will require a tremendous quantity of meat to satiate them.

ואתה אמרת בשר אתן להם ואכלו חודש ימים, if so, this will amount to a huge amount, as also described in Psalms 78,27 וימטר עליהם כעפר שאר וכחול ימים עוף כנף, “He rained meat on the like dust, winged birds like the sand of the sea.”

'ויאמר משה שש מאות אלף וגו, “Moses said: six hundred thousand (men plus their families You will provide with meat?)” Many people are appalled at how Moses apparently questioned G–d’s ability to provide the people with such an amount of meat. This is why hagaon ha-rav Nissim suggests the following interpretation of this verse. Moses asked that while he was well aware of G–d’s ability to provide a quantity of meat to last the people for 30 days, but that seeing this meat was not provided by G–d as a gift but in order to make the meat something that revolted them, what was the point in letting so much meat rot, after a day or two, seeing they had no means to keep it edible? Not only that, but how could they collect all that meat in the single day that it materialized for them? Moses drew a comparison when he spoke about the fish in the ocean, saying that even if all of them could be trapped in a single net, no one could remove sufficient fish from that net in a single day to last the nation for thirty days.