God gives the Israelites food
The Israelites left Elim and arrived in the wilderness (area with no cities or towns) of Sin. This was about 30 days after they left Egypt.
 And they took their journey from Elim, and all the congregation of the children of Israel came unto the wilderness of Sin, which is between Elim and Sinai, on the fifteenth day of the second month after their departing out of the land of Egypt.
The Israelites were complaining about Moses and Aaron. They wanted more food to eat. They said it would have been better to stay in Egypt because they had a lot of food in Egypt.
 And the whole congregation of the children of Israel murmured against Moses and Aaron in the wilderness:
 And the children of Israel said unto them, Would to God we had died by the hand of the LORD in the land of Egypt, when we sat by the flesh pots, and when we did eat bread to the full; for ye have brought us forth into this wilderness, to kill this whole assembly with hunger.
From the La Vista Church of Christ web site
The Lord God knew the Israelites were
complaining. He told Moses that He would give the Israelites bread
everyday. The bread would fall down from heaven. The Israelites were
supposed to go out and pick up the bread everyday.
 Then said the LORD unto Moses, Behold, I will rain bread from heaven for you; and the people shall go out and gather a certain rate every day, that I may prove them, whether they will walk in my law, or no.
God said that on the sixth day, they should pick up twice as much bread.
 And it shall come to pass, that on the sixth day they shall prepare that which they bring in; and it shall be twice as much as they gather daily.
Moses and Aaron said that when the Israelites saw the bread from heaven, they would remember how the Lord God brought them out of Egypt. They would see the glory of the Lord. That means they would be able to see God working. They would want to worship God. Moses said that God had heard the Israelites complaining.
 And Moses and Aaron said unto all the children of Israel, At even, then ye shall know that the LORD hath brought you out from the land of Egypt:
 And in the morning, then ye shall see the glory of the LORD; for that he heareth your murmurings against the LORD: and what are we, that ye murmur against us?
God would give them meat to eat in the evening and bread to eat in the morning. Moses said again that God heard the Israelites complaining. Moses told Aaron to bring the Israelites closer.
 And Moses said, This shall be, when the LORD shall give you in the evening flesh to eat, and in the morning bread to the full; for that the LORD heareth your murmurings which ye murmur against him: and what are we? your murmurings are not against us, but against the LORD.
 And Moses spake unto Aaron, Say unto all the congregation of the children of Israel, Come near before the LORD: for he hath heard your murmurings.
When Aaron was talking to the Israelites, they could see the glory of the Lord God in a cloud.
 And it came to pass, as Aaron spake unto the whole congregation of the children of Israel, that they looked toward the wilderness, and, behold, the glory of the LORD appeared in the cloud.
God talked to Moses. He said to tell the Israelites that He heard them complaining. He said that in the evening they would have meat to eat, and in the morning, they would have bread to eat. They would see that He was the Lord God.
 And the LORD spake unto Moses, saying,
 I have heard the murmurings of the children of Israel: speak unto them, saying, At even ye shall eat flesh, and in the morning ye shall be filled with bread; and ye shall know that I am the LORD your God.
In the evening, there were quails (wild birds) to eat. In the morning, there was dew on the ground. When the dew dried, there was special bread on the ground.
 And it came to pass, that at even the quails came up, and covered the camp: and in the morning the dew lay round about the host.
 And when the dew that lay was gone up, behold, upon the face of the wilderness there lay a small round thing, as small as the hoar frost on the ground.
The special bread was called manna. Moses told the Israelites that God said they should pick it up. They should measure what they picked up. Each person should have exactly an omer to eat. An omer was a little more than 2 quarts.
 And when the children of Israel saw it, they said one to another, It is manna: for they wist not what it was. And Moses said unto them, This is the bread which the LORD hath given you to eat.
 This is the thing which the LORD hath commanded, Gather of it every man according to his eating, an omer for every man, according to the number of your persons; take ye every man for them which are in his tents.
Each person was to eat all of his manna for the day. They should not leave any of it.
 And the children of Israel did so, and gathered, some more, some less.
 And when they did mete it with an omer, he that gathered much had nothing over, and he that gathered little had no lack; they gathered every man according to his eating.
 And Moses said, Let no man leave of it till the morning.
The Israelites did not totally obey Moses. Some of the Israelites did not eat all of their manna. During the night, worms got in the manna, and it smelled bad. Moses was mad at them about this.
 Notwithstanding they hearkened not unto Moses; but some of them left of it until the morning, and it bred worms, and stank: and Moses was wroth with them.
Everyone gathered the manna in the morning. After the sun became hot, the manna melted.
 And they gathered it every morning, every man according to his eating: and when the sun waxed hot, it melted.
Every sixth day, they gathered 2 omers for each person. On that day, they were supposed to eat 1 omer and keep the 2nd omer for the seventh day, the sabbath. They were supposed to rest on the sabbath. They were not to work to gather the manna on the sabbath.
 And it came to pass, that on the sixth day they gathered twice as much bread, two omers for one man: and all the rulers of the congregation came and told Moses.
 And he said unto them, This is that which the LORD hath said, To morrow is the rest of the holy sabbath unto the LORD: bake that which ye will bake to day, and seethe that ye will seethe; and that which remaineth over lay up for you to be kept until the morning.
In this situation, the manna did not have worms and smell bad during the night. That is because this was God's law for the sabbath day.
 And they laid it up till the morning, as Moses bade: and it did not stink, neither was there any worm therein.
 And Moses said, Eat that to day; for to day is a sabbath unto the LORD: to day ye shall not find it in the field.
 Six days ye shall gather it; but on the seventh day, which is the sabbath, in it there shall be none.
Some of the Israelites did not obey. On the sabbath, they were hungry and went out to look for manna on the ground. But there was none.
 And it came to pass, that there went out some of the people on the seventh day for to gather, and they found none.
The Lord was not happy about the Israelites who did not obey Him. He said again that they should rest on the sabbath. Then the Israelites obeyed Him.
 And the LORD said unto Moses, How long refuse ye to keep my commandments and my laws?
 See, for that the LORD hath given you the sabbath, therefore he giveth you on the sixth day the bread of two days; abide ye every man in his place, let no man go out of his place on the seventh day.
 So the people rested on the seventh day.
The manna was white, and it tasted like wafers (thin cookies) made with honey.
 And the house of Israel called the name thereof Manna: and it was like coriander seed, white; and the taste of it was like wafers made with honey.
The Lord told Moses to keep some manna for the future. People in the future would always be able to see how God gave the Israelites food.
 And Moses said, This is the thing which the LORD commandeth, Fill an omer of it to be kept for your generations; that they may see the bread wherewith I have fed you in the wilderness, when I brought you forth from the land of Egypt.
 And Moses said unto Aaron, Take a pot, and put an omer full of manna therein, and lay it up before the LORD, to be kept for your generations.
Aaron kept some manna for the future. The
Israelites ate manna for 40 years until they arrived in Canaan.
 As the LORD commanded Moses, so Aaron laid it up before the Testimony, to be kept.
 And the children of Israel did eat manna forty years, until they came to a land inhabited; they did eat manna, until they came unto the borders of the land of Canaan.
 Now an omer is the tenth part of an ephah.