Parshas Bamidbar

Posuk 1:2 says, you should count Bnei Yisrael ‘bimispar sheimos’ counting the names. Later we find, in posuk 3:15, when Hashem said to count the leviim it does not say ‘bimispar sheimos’. Why by the leviim does it not use the same wording?

When we counted Bnei Yisrael, we were counting from 20 years old and up, when a person has made a name for himself.  However, by the leviim they were counted from 30 days old, when a person has not accomplished anything and hasn’t earned his name.