KAṬHA UPANISHAD · 2.3.8

अव्यक्तात्तु परः पुरुषो व्यापकोऽलिङ्ग एव च ।
यं ज्ञात्वा मुच्यते जन्तुरमृतत्वं च गच्छति ॥ ८॥

avyaktāttu paraḥ puruṣo vyāpako’liṅga eva ca ।
yaṃ jñātvā mucyate janturamṛtatvaṃ ca gacchati ॥ 8॥

But highest above the Unmanifest is the Purusha who pervadeth all and alone hath no sign nor feature. Mortal man knowing Him is released into immortality.