Here is a third recorded incident of murmuring from the Israelites after they left Egypt. They crave "the good old days"! I find it incredible and sad that these people valued their comfort more than their freedom (and so it is with many today, particularly spiritually)! They would have rather been well-fed slaves than free people with some challenges. They affirm they would have preferred death in Egypt to hunger in the wilderness, but they are not thinking properly (and neither is any Christian who thinks that it would be better to return to slavery in the world; cf. II Pet. 2:20-22). Have they forgotten about the power of the God they serve (cf. Psa. 106)?
"Then the LORD said to Moses, 'Behold, I will rain bread from heaven for you. And the people shall go out and gather a certain quota every day, that I may test them, whether they will walk in My law or not. And it shall be on the sixth day that they shall prepare what they bring in, and it shall be twice as much as they gather daily'" (Exo. 16:4,5).
God replies again with patience. He knows this nation of a couple million people needs food in the wilderness. He will miraculously provide their sustenance for approximately forty years. However, in the blessing they received there would also be a test (as is often the case with blessings; e.g., I Tim. 6:17-19). Would they obey God and trust Him in receiving bread from heaven in the manner He would prescribe?
Moses then explains to the people a significant truth: When they complained against the divinely-appointed human leaders, they were really complaining against God Himself! They never seem to fully grasp this lesson, as their continued murmuring proves (e.g., Num. 16). God declared to Moses in Exodus 16:12 - "I have heard the complaints of the children of Israel. Speak to them, saying, 'At twilight you shall eat meat, and in the morning you shall be filled with bread. And you shall know that I am the LORD your God." God would bless them in a new way. They would be reminded yet again of Who was providing for them. They owed God a great debt of gratitude, not murmuring!
"So it was when the quails came up at evening and covered the camp, and in the morning the dew lay all around the camp. And when the layer of dew lifted, there, on the surface of the wilderness, was a small round substance, as fine as frost on the ground. So when the children of Israel saw it, they said to one another, 'What is it?' For they did not know what it was. And Moses said to them, 'This is the bread which the LORD has given you to eat. This is the thing which the LORD has commanded: "Let every man gather it according to each one's need, one omer for each person, according to the number of persons; let every man take for those who are in his tent"'" (Exo. 16:13-16).
From what I've read, an omer is just over a half-gallon of volume, though we cannot know the weight of this amount of food since manna is not available today for us to calculate density. God knew an omer per day per person would be about right, and He provided their daily omer (cf. Matt. 6:11)! Manna would be collected six days a week, according to the number of people in each family. Manna was distinct from anything they had seen before. What an amazing thing it would have been to eat quail that came right to the camp at night in a plentiful way! Even more incredible still would it have been to gather the sweet, flaky bread off the ground those first few weeks or months (until it started to become commonplace and taken for granted).