Bhagavad Gītā Chapter Four verse 17

karmaṇo hyapi boddhavyaṃ boddhavyaṃ ca vikarmaṇaḥ |
akarmaṇaśca boddhavyaṃ gahanā karmaṇo gatiḥ ||

karman - act, action, performance; any religious act or rite

Commentaries and Reflections

TKV Desikachar:

Karma is the means to know oneself.