How do we know that Jesus must be lifted up to provide salvation?

In John 3:14-15, Jesus refers to the account of Moses lifting the brazen serpent in Numbers 21 as a foreshadowing of His own crucifixion. Just as the Israelites were instructed to look at the lifted serpent to be healed from their snake bites, so must Jesus be lifted up on the cross to provide eternal life to those who believe in Him. This divine necessity underscores God's justice and mercy, as it allows sinners to be justified through faith in Christ's sacrificial death, fulfilling God's righteous requirement.