Bhagavad Gītā Chapter Six verse 20

yatroparamate cittaṃ niruddhaṃ yogasevayā |
yatra cāivātmanā ’tmānaṃ paśyann ātmani tuṣyati ||

ātman - essence; the highest personal principle of lifecitta - psyche; mind; heartnirodha - to contain, enclose, confine, restrainca - andeva - thus

Commentaries and Reflections

TKV Desikachar:

Before I inquire into who am I,
I must first look at who I am.