B.G 10.21
ādityānām ahaṁ viṣṇuḥ, jyotiṣām raviḥ aṁśumān. marīciḥ marutām asmi, nakṣatrāṇām ahaṁ śaśī ॥21॥
Among the Ādityas, I am Viṣṇu; among luminous bodies, I am the radiant Sun; among the Maruts, I am Marīci; among the stars, I am the Moon.
Gīta Bhāshya 10.21
He is called 'Viṣṇu' because he is the: mover of all beings and creatures, pervades the heavens and the earth, supreme splendor, dwells in the beings, their intentionality, and traverser. Root 'viṣlṛ' means to pervade, and 'viśa' means to enter.
viṣṇuḥ sarva-vyāpitva-praveśitva-ādeḥ.
He is called 'Viṣṇu' because of his all-pervading and penetrative nature.
"viṣlṛ vyāptau, viśa praveśane"
"'viṣlṛ' means to pervade, and 'viśa' means to enter."
iti ca paṭhanti.
- thus is the recitation.
"gatiś-ca sarva-bhūtānāṁ prajānāṁ ca-api bhārata. vyāptau me rodasī pārtha kāntiś-ca-abhyadhikā mama॥ adhibhūta-niviṣṭaś-ca tad-icchuś-ca-asmi bhārata. kramaṇāt-ca-api-ahaṁ pārtha viṣṇuḥ-iti-abhi-saṁjñitaḥ॥"
"O Bhārata, I am the mover of all beings and creatures; I pervade the heavens and the earth; my splendor is supreme; I dwell in the beings and am their intentionality too; and I traverse - O Pārtha, Hence I am known as Viṣṇu."
iti mokṣa-dharme ॥21॥
- stated thus in the Mokṣa-dharma section (of the Mahābhārata).