Sifrei Devarim
"and bailiffs for your tribes": wielders of the lash, viz. (II Chronicles 19:11) "and the Levite bailiffs before you," and (Nechemiah 8:11) "and the Levites silenced all the people."
Sifrei Devarim
R. Yehudah says: Whence is it derived that one is appointed over all? From "shall you appoint for yourself."