Exodus 16 - 18

God has just warned the people not to disobey Him but they strike out from beside the springs of living water and set off for the Desert of Sin, like the disobedient children they were. The immediately begin to sin also, grumbling about Moses and their plight.
My son spent some time in this very desert on the Arabian Penninsula a few years back during his Army service. He brought back pictures of camels running on the sandy, rocky terrain with just a few sprigs of vegetation here and there. I asked him how in the world they survived there with so little to eat. That is exactly what the Hebrews are grousing about at the beginning of Exodus 16. They wonder how they will eat. So God promises to send them food every morning. The food is an object lesson about our dependence on God. The manna would come down like snowflakes every morning and they were to gather only enough to feed them and their family through each day, except on the sixth day, when they would gather enough for two days so they could rest and worship God the following day. That is what we are supposed to do also. We are supposed to work hard six days a week, then spend one day resting and thanking God for what He has provided for us all week. Everyone needs at least one day a week to do this, or we become cranky and disorganized.
God sent bread from heaven in the mornings and caused quail to fly into the camp of the Israelites every evening so they would have plenty to eat and a variety of food. Instructions for the manna were to take an omer (about 2 quarts) for each person in the family and none was to be kept until the next day or it would spoil. Of course, some of them tried to gather more than they needed and it did spoil. It had maggots and it stank, which made Moses mad at them. Some of them also tried to gather manna on the day of rest, but there was none.
The Hebrew word manna means “what is it?” because the people had never seen anything like it. It was white and tasted good, like honey. An omer was kept to commemorate God feeding his people in the desert. The saved jar of manna was later placed in the Ark of the Covenant and I believe we will see this Ark again after the rapture.
The Israelites weren't aware at that time they would be eating manna for the next 40 years. The Lord led them on a very circuitous path out of Egypt because He knew they needed to learn many lessons before reaching the land they would settle in. Their next trial would be a lack of water. Again they grumbled and moaned about being thirsty. They thought they were going to die of thirst. They were threatening to stone Moses. God tells him to use his miracle working staff again to bring water from a rock in the sight of the tribal elders. Jesus is the rock that Moses is to strike with his staff, symbolizing the scourging He would later receive from the descendants of the elders when He becomes Living Water.
Their first challenge from the inhabitants of the land came in the desert in the form of attacking Amalekites at Rephidim. Moses knew there was power in the staff God gave him, so he promised to stand on top of a hill with the staff raised to God during the battle. As long as Moses held the staff skyward, the Hebrews were winning the fight, but when his arms tired and the staff was lowered, the Amalekites got the upper hand. So his brothers, Aaron and Hur came alongside Moses to help him hold the staff up until the battle was won by the Hebrew Army. Joshua was the general commanding the fight for the Hebrews.
God instructed Moses to write an account of the battle so it could be remembered because He had plans to completely obliterate the Amalekites. Until recently, scholars scoffed at the mention of Amalekites in the Bible, saying no archaeological evidence of such a people had ever been found. There has now been found artifacts with the inscription of Amalek. Moses built an altar on the location of the battle to give the glory to God.
Moses was separated from his wife and family when he returned to Egypt to lead the Hebrews out. His father-in-law has heard of all the exploits and knows Moses is nearby, so he brings his wife and two sons out to him.
Jethro, Moses' father-in-law, was a priest, but probably worshiped many Gods. Upon hearing all the Lord did for the Israelites to bring them out of Egypt, he became a believer in the one true God. Jethro observed all that Moses was trying to do for his people. Being older and wiser, he advised Moses to appoint officials to serve under him and deal with the people in groups with Moses representing them to God. Moses took Jethro's advice and the system he set up is the model for our own system of courts and judges today. Then, like a good father-in-law, Jethro went home.