The people departed from the place of twelve springs and seventy fruit producing palms and came to the wilderness of Sin. It is appropriately named because there they sinned against the Lord; the whole congregation of the sons of Israel grumbled against Moses and Aaron for taking them out of Egypt. They believed that they were better off in Egypt than to die of hunger in the wilderness.
This was sin against the Lord because it was the Lord who took the sons of Israel out of Egypt and brought them into the wilderness; therefore, it was the Lord whom they grumbled against. The Lord told Moses that for six days, in the morning he will rain bread from heaven and in the evening he will provide meat. However, the Lord did this to test the sons of Israel, whether they would listen to his commands or not. The Law does not justify anyone but gives us the knowledge of sin; the Law closes our mouth and makes us accountable to God. (cf. Rom. 3:19, 20) The Law shows us that we need the mercy and grace of God to be justified in his sight. (cf. Gal. 3:24)
The Lord gave a new commandment regarding the gathering of bread rained from heaven in the morning and the meat in the evening. This commandment was given to test the sons of Israel. In the evening, the Lord covered the camp with quails, and in the morning, he covered the camp with a flake like substance. It was said to be like coriander seed, white, and it tasted like a sweet wafer. The commandment of the Lord regarding the bread from heaven and the quails was that they each gather no more than they could eat on that day, but on the sixth day, each was to gather enough for two days, and rest on the seventh day.
Did they do as the Lord commanded? Some gathered more than they needed for a single day and what was leftover spoiled during the night, so, nonetheless, they had to gather again the next day. Some did not gather twice as much on the sixth day as the Lord commanded; therefore, they went out looking on the seventh day. The people failed to observe the commandment of the Lord. This is how the sabbath rest was established. It was a test. Would the sons of Israel trust the Lord to provide daily for their needs, provide twice as much as they needed on the sixth and would they rest on the seventh day?
The amount needed for a single day was an omer: “a handful, one-tenth of an ephah=half a gallon dry measure.” (EBD) The people named the flake like substance manna. The Lord commanded Moses and Aaron to keep an omerful of it, in a jar, throughout their generations as a remembrance of the Lord’s provision in the wilderness. Aaron would place it before the testimony, which at this point in the story is yet to come. The sons of Israel lived on the manna provided by the Lord for forty years.