Bemidbar details a census of Bnei Yisrael and a separate one for the Leviim. Commentators notice that by far the smallest of the tribes is Levi. Why is that? We look at a few explanations, some relating to the experience of enslavement in Egypt.
One opinion is that the Book of Shemot mentions that as Israel was oppressed, they multiplied - but Levi was not enslaved. Another opinion is that a higher spiritual level is usually associated with a rarer commodity, or with less material success. Or perhaps it was a favor to the Tribe of Levi so that they could be sustained with limited space and resources allocated to them.