Bhagavad Gita · 8.13

ओमित्येकाक्षरं ब्रह्म व्याहरन्मामनुस्मरन्।यः प्रयाति त्यजन्देहं स याति परमां गतिम्॥

om ity ekākṣharaṁ brahma vyāharan mām anusmaran yaḥ prayāti tyajan dehaṁ sa yāti paramāṁ gatim

Uttering the single syllable Om, which is Brahman, and remembering Me, whoever departs leaving the body attains the supreme destination.

— Bhagavad Gita 8.13

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