Matsya Purana — Tārakāsura’s Austerity and Boon; Mobilization for War; Bṛhaspati’s Fourfold P...
रक्षितुं नैव शक्नोति चपलश्चपलाः श्रियः तच्छ्रुत्वा दानवाः सर्वे वाक्यं तस्यासुरस्य तु //
rakṣituṃ naiva śaknoti capalaścapalāḥ śriyaḥ tacchrutvā dānavāḥ sarve vākyaṃ tasyāsurasya tu //
The restless man cannot truly safeguard the restless fortunes of Śrī (prosperity). Hearing the words of that Asura, all the Dānavas listened and took heed.
It does not speak directly about Pralaya; it teaches a moral principle: prosperity (Śrī) is inherently unstable, and an unsteady person cannot preserve what is already fickle.
It implies that steadiness (self-control, consistent policy, disciplined conduct) is essential for preserving wealth and royal fortune; a capricious ruler/householder loses prosperity because both the mind and fortune become unstable.
No Vāstu/ritual rule is stated; the takeaway is ethical: auspicious prosperity is maintained through stability and restraint—qualities also valued in ritual discipline and orderly governance.