Matsya Purana — Agastya’s Origin
यस्माज्जीवनिकायस्य महतः संक्षयो भवेत् तस्मान्न पापमद्यावां करवाव पुरंदर //
yasmājjīvanikāyasya mahataḥ saṃkṣayo bhavet tasmānna pāpamadyāvāṃ karavāva puraṃdara //
Since this would cause a great destruction of living beings, therefore, O Purandara, let us not commit this sin.
It does not describe cosmic Pralaya directly; it uses the idea of “great destruction of living beings” as an ethical reason to avoid an act that would cause widespread loss of life.
It frames dharma as preventing large-scale harm: a ruler or householder should avoid actions that lead to the ruin of many beings, choosing restraint and compassion over expedient but sinful outcomes.
No Vāstu, temple-building, or ritual procedure is specified; the takeaway is a general dharmic principle—avoid any undertaking that results in broad harm to living creatures.