Bhagavad Gita: Chapter 2, Verse 25

अव्यक्तोऽयमचिन्त्योऽयमविकार्योऽयमुच्यते ।
तस्मादेवं विदित्वैनं नानुशोचितुमर्हसि ॥ २-२५ ॥

avyakto ’yam acintyo ’yam avikāryo ’yam ucyate
tasmād evaṁ viditvainaṁ nānuśocitum arhasi  2.25

It is said that the soul is unmanifest, inconceivable, unchangeable. Therefore, knowing this, you should not grieve for the body.