Bhagavad Gita
2.25

अव्यक्तोऽयमचिन्त्योऽयमविकार्योऽयमुच्यते | तस्मादेवं विदित्वैनं नानुशोचितुमर्हसि ||२५||

avyakto'yam achintyo'yam avikāryo'yam uchyate tasmād evaṁ viditvainaṁ nānuśhochitum arhasi

Translation

It is said that the soul is invisible, inconceivable, immutable, and unchangeable. Knowing this, you should not grieve for the body.

Interpretation

The soul is 'avyakta' (unmanifest — beyond the reach of the senses), 'achintya' (inconceivable — beyond the grasp of the ordinary mind), and 'avikārya' (immutable — it cannot be altered by experience). Knowing this, Krishna says: you should not grieve. Grief about the death of the body reveals ignorance of what the body actually is and what the soul actually is.