B.G 8.17, 18, 19 and 20
सहस्रयुगपर्यन्तमहर्यद्ब्रह्मणो विदुः। रात्रिं युगसहस्रान्तां तेऽहोरात्रविदो जनाः ॥१७॥
sahasrayugaparyantamaharyadbrahmaṇo viduḥ। rātriṁ yugasahasrāntāṁ te'horātravido janāḥ ॥17॥
Those who know the nature of day and night understand that the day of Brahmā lasts for a thousand yugas, and his night also ends after a thousand yugas.
अव्यक्ताद् व्यक्तयः सर्वाः प्रभवन्त्यहरागमे। रात्र्यागमे प्रलीयन्ते तत्रैवाव्यक्तसञ्ज्ञके ॥१८॥
avyaktād vyaktayaḥ sarvāḥ prabhavantyaharāgame। rātryāgame pralīyante tatraivāvyaktasañjñake ॥18॥
From the unmanifest, all manifest beings arise at the beginning of the day (of Brahmā), and at the arrival of the night, they dissolve back into that which is called the unmanifest.
भूतग्रामः स एवायं भूत्वा भूत्वा प्रलीयते। रात्र्यागमेऽवशः पार्थ प्रभवत्यहरागमे ॥१९॥
bhūtagrāmaḥ sa evāyaṁ bhūtvā bhūtvā pralīyate। rātryāgame'vaśaḥ pārtha prabhavatyaharāgame ॥19॥
O Pārtha (Arjuna), this multitude of beings, being born again and again, dissolves at the arrival of the night (of Brahmā) helplessly, and at the arrival of the day, it comes into existence again.
परस्तस्मात्तु भावोऽन्योव्यक्तो व्यक्तात् सनातनः। यः स सर्वेषु भूतेषु नश्यत्सु न विनश्यति ॥२०॥
parastasmāttu bhāvo'nyovyakto vyaktāt sanātanaḥ। yaḥ sa sarveṣu bhūteṣu naśyatsu na vinaśyati ॥20॥
But beyond that unmanifest (existence), there is another eternal unmanifest reality, which does not perish even when all beings perish.
Gīta Tātparya 8.17, 18, 19 and 20
The Supreme Brahman is not destroyed when the dissolution of all manifested beings occurs. 'sahasra' - many or infinite. 'brahmaṇa' - the Supreme Brahman.
"Sahasram" (a thousand) signifies multitude or infinite. It word 'brahmaṇa' refers to the Supreme Brahman.
"All manifest beings arise from the unmanifest at the arrival of the day. At the arrival of the night, they dissolve into that very unmanifest, which is so designated."
- stated thus in the remainder of the statement.
Indeed, the Brahman is not destroyed when the dissolution of all manifested beings occurs.
"Even though Lord Hari is eternal, His time is considered in terms of two parārddhas each for a day and night. It is indeed a mere blink of an eye for the inactive One."
- stated thus as well.
