Matsya Purana — Manvantaras
अथर्वऋग्यजुःसाम्नां वेदेष्विह पृथक्पृथक् ऋषीणां तप्यतां तेषां तपः परमदुश्चरम् //
atharvaṛgyajuḥsāmnāṃ vedeṣviha pṛthakpṛthak ṛṣīṇāṃ tapyatāṃ teṣāṃ tapaḥ paramaduścaram //
Here, within the Vedas—Atharva, Ṛg, Yajus, and Sāman—each stream stands distinct. For those seers who undertook austerities, their tapas was supremely difficult to perform.
It does not describe Pralaya directly; it emphasizes that Vedic knowledge is divided into distinct Vedas and that such revelation is grounded in the extraordinary tapas of the ṛṣis.
By affirming the Vedas as distinct authorities attained through severe tapas, it implies that royal and household dharma should be guided by Vedic injunctions (śruti) and respected as hard-won, authoritative knowledge.
No direct Vāstu or iconographic rule is stated; the ritual takeaway is that Vedic rites (yajña, mantra-prayoga) derive legitimacy from the separately preserved Vedic traditions and the ṛṣis’ disciplined realization.