Nadab and Abuhu were burning incense in the Tent of Meeting when they died. The fire was called strange or unholy because God had not ordered it. The Lord was not pleased that they had done this and set fire upon them and they were consumed. (Leviticus 10:1-2) People who are living outside of the will of God can be consumed by this behavior.
Nadab and Abuhu were priest had had been ordained by their father Arron but they were not serving the Lord in obedience. This was dishonorable to God. God is the Creator of all that exist and is a holy and righteous God. He expects that we His creation should always honor Him.
Arron and his two remaining sons were priest and the rest of the Levite tribe were their servants. The servants help the priest to look after and care for the Tent of Meeting. There were two main task to their duties. Whenever the Israelites moved the Levite tribe had to take down the tent and carry it to the next destination and set it back up. This was their responsibility and it was hard work.
They also had to attend to the tent. If any other than they came to close to the tent they would die. Not only that but because of their disobedience not only would they be punished by death but all of the Israelites would suffer. (Numbers 1:53; 16:40; 25:8)
The first born males of the animals and also the first born males of the people belonged to God. The Israelites had to redeem both their animals and their sons. (Exodus 13:1-2) Redemption was effected by means of a sacrifice or a payment of money.
During the time that God was giving Moses the law while he was up on Mount Sinai the Israelite people made an idol out of gold in the image of a calf. (Exodus 32) Only the Levite tribe remained loyal to God. God granted the privilege of serving Him to the Levite tribe. So the Levite tribe served God exclusively.
God told Moses to take a census of the Levite tribe who were one month old or older. The men of the Levite tribe were to help the priest to do this. Moses did what God had told him to do and counted the Levite tribe by clan. Moses told each clan where to camp.
The priest camped on the east side of God’s Tent and Kohath’s clan camped on the south side. Kohath’s clan was the biggest and they had the responsibility of the special furniture of God’s Tent.
Gershon’s clan camped on the west side of God’s Tent and they were responsible for the covers, curtains and ropes. Merari’s clan was the smallest and they camped on the north side of God’s Tent. They looked after all the parts of the tents frame and the things in the yard surrounding the tent. Whenever the Israelites traveled the clans of the Levites had to carry the parts of God’s Tent that they were responsible for.
Moses was now told to count the first born male of all the Israelite people. He also had to collect five pieces of silver for each first born. Five pieces of silver was the price of a slave at that time and it was a lot of money. Many of the people earned less than one piece of silver in a month. We do not know who paid the five pieces of silver but it might have been the first born themselves. We don’t know but Moses did as God had told him to do. Silver was the money of the day and a piece weighed about 11.5 grams. (Verse 47)