Matsya Purana — Characteristics of Dvāpara and Kali Yugas
ततः प्रवर्तिते तासां प्रजानां द्वापरे पुनः लोभो धृतिर्वणिग्युद्धं तत्त्वानाम् अविनिश्चयः //
tataḥ pravartite tāsāṃ prajānāṃ dvāpare punaḥ lobho dhṛtirvaṇigyuddhaṃ tattvānām aviniścayaḥ //
Then, when those peoples come to be established again in the Dvāpara Yuga, greed arises; steadfastness becomes bound up with trade and conflict, and there is no clear ascertainment of the true principles (tattvas).
It does not describe Pralaya directly; instead, it characterizes the post-establishment of society in the Dvāpara Yuga, highlighting ethical and intellectual decline (greed and uncertainty about tattvas).
By warning that Dvāpara society tends toward greed and trade-driven conflict, it implies a king must restrain avarice, regulate commerce and disputes, and uphold dharma so that people regain clarity about right conduct and truth.
No explicit Vāstu or ritual procedure is stated; the takeaway is contextual—when tattva-understanding declines, ritual and temple practice can become mechanical, so texts urge rulers and householders to preserve correct doctrine and disciplined conduct.