Srimad-Bhagavatam: Canto 12 - Chapter 1 - Verse 5
Sanskrit:
द्विपरार्धे त्वतिक्रान्ते ब्रह्मण: परमेष्ठिन: ।तदा प्रकृतय: सप्त कल्पन्ते प्रलयाय वै ॥ ५ ॥
ITRANS:
dvi-parārdhe tv atikrāntebrahmaṇaḥ parameṣṭhinaḥtadā prakṛtayaḥ saptakalpante pralayāya vai
Translation:
When the two halves of the lifetime of Lord Brahmā, the most elevated created being, are complete, the seven basic elements of creation are annihilated.