What kind of serpent did God tell Moses to lift up in the wilderness, and what did it do?
God instructed Moses to erect a brazen serpent in the wilderness. When the snake-bitten Israelites looked upon it, that serpent judged their sin. Brass throughout Scripture speaks of judgment, and the cross was the reality where sin was judged. Thus sin was judged.
Les explains that brass always speaks of judgment all through Scripture. He recalls when Israel was dying from snakebites, and God told Moses to erect a brazen serpent. As the people looked at that serpent, it judged their sin. Les connects this to the cross, asking what the reality of the work of the cross was: sin was judged. Therefore everything regarding the judgment of sin is denoted with the metal brass. The brazen altar was made of acacia wood covered with brass, and later the laver of cleansing was also made of brass from the women's looking glasses.