Bhagavad Gita Chapter 15, Verse 16

द्वाविमौ पुरुषौ लोके क्षरश्चाक्षर एव च | क्षरः सर्वाणि भूतानि कूटस्थोऽक्षर उच्यते ||

dvāv imau puruṣau loke kṣaraś cākṣara eva ca kṣaraḥ sarvāṇi bhūtāni kūṭa-stho 'kṣara ucyate

There are two purushas in this world: the perishable and the imperishable. All beings are perishable, and the unchanging is called the imperishable.

Krishna introduces the fundamental distinction: 'Dvāv imau puruṣau loke kṣaraś cākṣara eva ca'—there are two purushas in this world: the perishable and the imperishable. This is the key distinction that sets up understanding Purushottama. 'Kṣaraḥ sarvāṇi bhūtāni'—all beings are perishable. Everything in the material world—all bodies, all material existence—is perishable, temporary. 'Kūṭa-stho 'kṣara ucyate'—the unchanging is called the imperishable. Kutastha is the unchanging witness—the soul that remains unchanged while the body changes. This is the imperishable—not the body, but the soul. Understanding this distinction is crucial: the perishable (all material beings) and the imperishable (the unchanging soul). This sets up the next verse which reveals the third—Purushottama, who transcends both.