Matsya Purana — Catalogue of the Eighteen Puranas
यत्राधिकृत्य गायत्रीं वर्ण्यते धर्मविस्तरः वृत्रासुरवधोपेतं तद्भागवतमुच्यते //
yatrādhikṛtya gāyatrīṃ varṇyate dharmavistaraḥ vṛtrāsuravadhopetaṃ tadbhāgavatamucyate //
That scripture in which, taking the Gāyatrī as the governing foundation, the full expanse of Dharma is set forth, and which also includes the account of the slaying of Vṛtrāsura, is called the Bhāgavata.
This verse does not describe pralaya directly; instead, it defines a Bhāgavata-type scripture by its dharma-focused teaching grounded in Gāyatrī and by including major Vedic-Purāṇic episodes like the Vṛtrāsura slaying.
By stating that a Bhāgavata text is characterized by a broad exposition of dharma, it implies that rulers and householders should treat such scripture as an authoritative guide for righteous conduct, governance, vows, and ethical discipline.
The ritual significance is the primacy of Gāyatrī—presented as a foundational mantra/metre for dharma-teaching; no specific Vāstu or temple-building rule is referenced in this verse.