Bhagavad Gita · 13.13

ज्ञेयं यत्तत्प्रवक्ष्यामि यज्ज्ञात्वामृतमश्नुते।अनादिमत्परं ब्रह्म न सत्तन्नासदुच्यते॥

jñeyaṁ yat tat pravakṣhyāmi yaj jñātvāmṛtam aśhnute anādi mat-paraṁ brahma na sat tan nāsad uchyate

I shall now describe that which is to be known, knowing which one attains immortality: the beginningless supreme Brahman, which is said to be neither existence nor non-existence.

— Bhagavad Gita 13.13

Source: Sacred-Texts.com (Sanskrit) + Bhagavad-Gita.io (translations)