Matsya Purana — Manvantaras
ऋषिस्तस्मात्परत्वेन भूतादिरृषयस्ततः ऋषिपुत्रा ऋषीकास्तु मैथुनाद्गर्भसम्भवाः //
ṛṣistasmātparatvena bhūtādirṛṣayastataḥ ṛṣiputrā ṛṣīkāstu maithunādgarbhasambhavāḥ //
Therefore, by virtue of their higher (spiritual) status they are called Ṛṣis; thereafter, the primordial sages beginning with Bhūta are so named. The Ṛṣīkās, however, are the daughters of Ṛṣis, born from sexual union and conceived in the womb.
It does not describe Pralaya directly; it classifies beings in creation by explaining how Ṛṣis are designated by spiritual eminence and how Ṛṣīkās arise through ordinary biological birth.
Indirectly, it supports dharma through lineage-clarity: kings and householders are taught to honor Ṛṣis as spiritually eminent authorities, while also recognizing the social-genealogical categories of descendants (such as Ṛṣīkās) within regulated family life.
No Vāstu or temple-rule is stated here; the ritual takeaway is the emphasis on Ṛṣi-status and lineage categories, which can affect who is honored in rites (e.g., guru/ṛṣi veneration) and how genealogies are recited in Purāṇic ritual contexts.