Exodus 16:2 - Ellicott's Commentary On The Whole Bible

The whole congregration... murmured. — This is the third “murmuring.” The first was at Pi-hahiroth, on the appearance of the host of Pharaoh (Exodus 14:11-12); the second was at Marah, when the water proved undrinkable (Exodus 15:24); the third, in the wilderness of Sin, was brought about by no special occurrence — unless it were the exhaustion of the supplies of grain which had been brought out of Egypt — but seems to have resulted from a general dissatisfaction with the conditions of life in the wilderness, and with the prospects which lay before them.