Sita Varma, Masked Racer

Legendary Creature — Human Rogue

Exhaust — : Put X +1/+1 counters on Sita Varma. Then you may have the base power and toughness of each other creature you control become equal to Sita Varma's power until end of turn. (Activate each exhaust ability only once.)

Exhaust abilities can be activated any time you could normally activate an ability.
If an exhaust ability of a permanent is activated, and then that permanent leaves the battlefield and returns to the battlefield, it becomes a new object so its exhaust ability can be activated again.
If an ability triggers whenever you activate an exhaust ability, that ability resolves before the exhaust ability resolves.