Parshas Chukas.
‘purifies those impure, and makes impure those pure’
(Chazal describing the Parah Hadumah).
This statement describes 2 ways, how the Parah Adumah represents the tactics needed to fight against the Yetzer Hara.
‘Makes impure those pure’
This signifies the Parah (Midas Hadin) of the Parah Aduma process.
The first tactic to fight against the Yetzer Hara of pride (a pure person) e.g. a Torah Scholar like Rabbi Elazar Ben Shimon in Talmud Taanis -who needed to become impure (not so proud about his learning which led him to insult someone)is to ‘remember the day of death (Talmud Brochos).
‘Makes pure those impure’
This signifies the Mayim Chaim (Midas Harachamim) of the Parah Adumah process.
On the other hand someone who is a Rasha (impure), needs to learn Torah (compared to Mayim Chaim) to make him a better person (pure).
(Ed Peri Tevuah)