I am the Self, oh Arjuna, situated in the heart of all beings. I am the beginning, the middle and the end of all beings.

The first vibhūti: the Lord as ātmā. Aham ātmā — I am the Self — the supreme ātman of all ātmans. Sarva-bhūtāśaya-sthitaḥ — situated in the heart of all beings — as paramātman.

Guḍākeśa — conqueror of sleep — Arjuna can understand this because he has conquered the ignorance of saṃsāra. Ādiḥ madhyaḥ antaḥ — beginning, middle and end — the Lord permeates all existence in time and space.

This is the most important vibhūti: the Lord as the inner Self of all.