Matthew Henry on Numbers 11:4-9

Man, having forsaken his proper rest, feels uneasy and wretched, though prosperous. They were weary of the provision God had made for them, although wholesome food and nourishing. It cost no money or care, and the labour of gathering it was very little indeed; yet they talked of Egypt's cheapness, and the fish they ate there freely; as if that cost them nothing, when they paid dearly for it with hard service! While they lived on manna, they seemed exempt from the curse sin has brought on man, that in the sweat of his face he should eat bread; yet they speak of it with scorn. Peevish, discontented minds will find fault with that which has no fault in it, but that it is too good for them. Those who might be happy, often make themselves miserable by discontent. They could not be satisfied unless they had flesh to eat. It is evidence of the dominion of the carnal mind, when we want to have the delights and satisfaction of sense. We should not indulge in any desire which we cannot in faith turn into prayer, as we cannot when we ask meat for our lust. What is lawful of itself becomes evil, when God does not allot it to us, yet we desire it.