The soul within the body is self-luminous and is separate from the visible gross body and invisible subtle body. It remains as the fixed basis of changing bodily existence, just as the ethereal sky is the unchanging background of material transformation. Therefore the soul is endless and without material comparison.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
न तत्रात्मा स्वयञ्ज्योतिर्यो व्यक्ताव्यक्तयोः परः । आकाश इव चाधारो ध्रुवोऽनन्तोपमस्ततः
na tatrātmā svayañjyotiryo vyaktāvyaktayoḥ paraḥ | ākāśa iva cādhāro dhruvo'nantopamastataḥ
SB 12.5.8