ମୁ ଜଣେ ଆତ୍ମା ବୋଲି କିପରି ଜାଣିବି?

Bg. 2.30
देही नित्यमवध्योऽयं देहे सर्वस्य भारत ।
तस्मात्सर्वाणि भूतानि न त्वं शोचितुमर्हसि ॥ ३० ॥
dehī nityam avadhyo ’yaṁ
dehe sarvasya bhārata
tasmāt sarvāṇi bhūtāni
na tvaṁ śocitum arhasi

Translation
O descendant of Bharata, he who dwells in the body can never be slain. Therefore you need not grieve for any living being.

The Svetasvatara Upanisad (5.9) confirms this:

kesagra-sata-bhagasya
satadha kalpitasya ca
bhago jivah sa vijneyah
sa canantyaya kalpate

“When the upper point of a hair is divided into one hundred parts and again each of such parts is further divided into one hundred parts, each such part is the measurement of the dimension of the spirit soul.”