Oxen and donkeys don't work well together

In Deuteronomy 22:10, the Israelites were commanded "Do not plow with an ox and a donkey yoked together." A common-sense idea that reflected the notion that plowing fields with a pair of different animals with different notions would be difficult. Once the animals were yoked together, they were stuck with each other despite their differences - and that invites conflict. Fifteen centuries later, Paul commands in 2 Corinthians 6:14 for Christians to "not be yoked with unbelievers." Christians and non-christians are different animals and, according to their different natures, it would be difficult to move them harmoniously in the right direction.

The Bronze Serpent

There is an interesting article at the following link describing and naming the sybolism found in Numbers 21. http://en.wikipedia.org/wiki/Nehushtan The sin of the Israelites led to death by the serpent. Healing came only from looking to the cross. This wonderful imagery is completed in Jesus's foretelling of his crucifixion in John 3:14-15.