Hiram opens up Numbers brilliantly here.
Three poles lifted up - Numbers 13-14 (the pole carrying the firstfruits); Numbers 16-17 (Aaron's budding staff) and Numbers 21 (the bronze serpent) - all types of Christ.
Read the whole thing, it's wonderful, nourishing stuff.
He's also got a great post on Christ's temptations here.
Which is good cos I'm preaching on them on Sunday.
Both of them take seriously the vicarious humanity of Christ. He is in the wilderness not to show us how we can defeat Satan but to actually do it for us, in our place, as our Representative. Check them out - very highly recommended!