John Calvin Commentary Exodus 16:13

"And it came to pass at even, that the quails came up, and covered the camp: and in the morning the dew lay round about the camp." — Exodus 16:13 (ASV)

And it came to pass. We shall afterwards see that when, from weariness of the manna, they began to desire meat, quails were again given them; but while the quails were still in their mouths, a terrible punishment was inflicted upon their gluttony. When, in this instance, they had only complained of their lack of food, God for once satiated them with flesh, that He might show them that He has in His hand all kinds and quantities of foods.

Yet, it was His will that they should be content with one single kind of food. For, although they had complained that they were deprived of flesh (unlike their situation at the pots they had formerly sat beside), it was not reasonable that He should comply altogether with their unholy desires. Besides, it was profitable for them that certain limits should be set, that they might learn dependence on His will.