Bhagavad Gita, Chapter 15, Verse 17

उत्तमः पुरुषस्त्वन्यः परमात्मेत्युदाहृतः । यो लोकत्रयमाविश्य बिभर्त्यव्यय ईश्वरः

uttamaḥ puruṣastvanyaḥ paramātmetyudāhṛtaḥ | yo lokatrayamāviśya bibhartyavyaya īśvaraḥ

Translation

But distinct is the Highest Spirit spoken of as the Supreme Self, the indestructible Lord who penetrates and sustains the three worlds.

— Alladi Mahadeva Sastri

Word meanings

uttamaḥ
the highest
puruṣaḥ
spirit
tu
indeed
anyaḥ
another
paramātmā
highest Self
iti
thus
udāhṛtaḥ
called
yaḥ
who
lokatrayam
triple world
āviśya
having entered
bibharti
sustains
avyayaḥ
the imperishable
īśvaraḥ
Lord

Śaṅkarācārya's commentary

The Highest Spirit is quite distinct from the two — the perishable and the imperishable — and untainted by the evils of those two upādhis. He is the Supreme Self. He is Supreme as compared with the other selves set up by avidyā, such as the physical body; and He is the Self as constituting the unfailing Inner Consciousness of all beings. He is therefore known as the Supreme Self in the Vedāntas (Upaniṣads). The Highest Spirit is further specified thus: He is the Eternal Omniscient Lord, Nārāyaṇa, who penetrates by His Vital Energy (Bala-Śakti) the three worlds — the Earth (Bhūḥ), the Mid-region (Bhuvaḥ) and Heaven (Suvaḥ) — and supports them by His mere existence in them.