Bhagavad Gita 15.16

द्वाविमौ पुरुषौ लोके क्षरश्चाक्षर एव च।क्षरः सर्वाणि भूतानि कूटस्थोऽक्षर उच्यते ॥१५.१६॥

dvāvimau puruṣau loke kṣaraścākṣara eva cakṣaraḥ sarvāṇi bhūtāni kūṭastho’kṣara ucyate

Two Purushas there are in this world: the perishable and the imperishable. All beings are perishable, and the Kutastha—the unchanging—is called the imperishable.

गीता