Sochatchov on Parshat Chukat

...Plus the Life and Times of the Avnei Nezer and Shem MiShmuel, the Sochatchover Rebbes

What is the rationale behind the prohibition for a Kohen to become tamei met? Why does immersing in a mikvah remove tumat met?

Why was he commanded to hit the rock the first time and speak the rock the second time? Why was he told to bring his staff?

Shiur provided courtesy of Torah Anytime