Bhagavad Gita: Chapter 15, Verse 6

न तद्भासयते सूर्यो न शशाङ्को न पावक: |
यद्गत्वा न निवर्तन्ते तद्धाम परमं मम || 6||

na tad bhāsayate sūryo na śhaśhāṅko na pāvakaḥ
yad gatvā na nivartante tad dhāma paramaṁ mama

na—neither; tat—that; bhāsayate—illumine; sūryaḥ—the sun; na—nor; śhaśhāṅkaḥ—the moon; na—nor; pāvakaḥ—fire; yat—where; gatvā—having gone; na—never; nivartante—they return; tat—that; dhāma—abode; paramam—supreme; mama—Mine

na tad bhasayate suryo na shashanko na pavakah
yad gatva na nivartante tad dhama paramam mama

Translation

BG 15.6: Neither the sun nor the moon, nor fire can illumine that Supreme Abode of Mine. Having gone There, one does not return to this material world again.

Commentary

Here, Lord Shree Krishna briefly describes his divine Abode, which he says is self-luminous. No sun, moon or fire is required to light it up. As the material realm is created by Maya (material energy), it is full of defects and dualities. Whereas, the divine realm is created by Yogmaya (spiritual energy), which is both transcendental and perfect. It is also described as sat-chit-ānand (full of bliss, knowledge, and eternality).

The Paravyom is the spiritual sky of the divine realm. It is filled with splendor and divine opulence. It contains numerous abodes of various eternal forms of God. Narayan, Ram, Shree Krishna, etc. all have their separate Abodes.  They reside there eternally along with their devotees and perform divine Leelas (Pastimes). In a prayer to Shree Krishna Brahma says:

goloka-nāmni nija-dhāmni tale cha tasya
devī maheśha-hari-dhāmasu teṣhu teṣhu
te te prabhāva-nichayā vihitāśh cha yena
govindam ādi-puruṣhaṁ tam ahaṁ bhajāmi
(Brahma Samhitā verse 43)

“In the spiritual sky is Golok, the personal Abode of Shree Krishna.  That spiritual sky also contains the Abodes of Narayan, Shiv, Durga, etc.  I adore Supreme Divine Personality Lord Krishna, by the majesty of whose opulence, this is possible.” Brahma has further described Golok in the following verse:

ānanda-chinmaya-rasa-pratibhāvitābhis
tābhir ya eva nija-rūpatayā kalābhiḥ
goloka eva nivasaty akhilātma-bhūto
govindam ādi-puruṣhaṁ tam ahaṁ bhajāmi
(Brahma Samhitā verse 37)

“I worship Govind, the Supreme Lord, who resides in Golok with the expansion of His own form, Radha.  Their eternal Associates are the sakhis, who are enlivened by the ever-blissful spiritual energy and are the embodiments of sixty-four artistic abilities.” 

Shree Krishna assures Arjun that souls who attain him, reside eternally with him in His Supreme Abode, which is perfect in every way. These devotees become free from samsara the cycle of birth and death and get to participate in His Divine Leelas.