The bronze serpent in Numbers is a symbol of Jesus being lifted up

What is the meaning of the sabbatical year and of the jubilee?
The word “sabbath” means “seven” in Hebrew. The sabbatical year was every seventh year. The land was allowed to lie fallow, at rest. From a natural viewpoint, this helped to replenish the land. But the practice was considered from the spiritual standpoint: As mankind rested on the Sabbath day each week, so the land would give glory to God by resting on the seventh year.
Nowadays a “sabbatical year” is a time when professionals take time off from their work. The word “jubal” in Hebrew means a “ram’s horn. From the blowing of the ram’s horn every “sabbath of sabbaths” (i.e. every fifty years), the word “jubilee” comes.
This was a special kind of sabbatical year. Debts were canceled; land was returned to its ancestral family; land could not be sold in perpetuity. Read about the sabbatical and the jubilee in Leviticus 25. Nowadays, we use the word “jubilee” for a special celebration that comes every certain number of years.
In the Church, the Holy Year is a “jubilee” coming every 25 years. In the Holy Year, pilgrimages to Rome are encouraged.

What does numbers say about the fidelity of the Israelites?
Beginning with chapter 11, Numbers tells several stories about the discontent and rebellion of the Israelites. Once again the story of the quail is told. It is basically the same story told in Exodus 16. Even Aaron and Miriam (Moses’ sister) rebelled against Moses.
In response to the rebellions, the Lord was going to abandon the people, but there is a beautiful story in Chapter 14: Moses reminds the Lord of his lovingkindness; he bargains with the Lord and the Lord forgives! But the impression of the entire book is one of constant rebellion against God, and God’s forgiving mercy.

Why did the Israelites wander about in the wilderness for 40 years?
The Book of Numbers says that the wandering was a punishment for their rebellion. Moses himself was not permitted to enter the “Promised Land,” since he had disobeyed God. Numbers 20 tells of the desire for water, and of God telling Moses to strike a rock and water would come forth. Moses struck the rock twice instead of once. Numbers implies that this was a symbol of disobedience.

What is the bronze serpent?
Numbers 21 describes a strange story. The Israelites had rebelled. Therefore fiery (i.e. “Seraph”) serpents were sent to bite them, and many died. The Israelites repented and cried to Moses for help. God told him to make a bronze serpent and mount it on a pole; whoever looked at the serpent would be healed.
To us this seems like magic or like idolatry, but we should try to see things in context of the times. The story is important to us for its symbolism and use by Jesus. In John’s gospel, Jesus says that he must be “lifted up” like the bronze serpent, and whoever looks to him will be saved. See John 3:14.
One other thing: Apparently this bronze serpent (called the Nehushtan) became an object of idolatry in the temple, and was smashed by good King Hezekiah in the 8th century B.C. See II Kings 18:4.

Who is Balaam?
Balaam was a pagan soothsayer or seer. Numbers 21-24 tells the strange story of Balaam. The Israelites were conquering the land. Balak, King of Moab, summoned Balaam to “prophesy” against Israel. (Prophecies were thought to produce their effect; they could be blessings or curses.) Balaam tried to do so, but was prevented. Read this strange story of Balaam and his talking donkey!