Matsya Purana — Characteristics of Dvāpara and Kali Yugas
वर्णाश्रमपरिभ्रष्टाः संकरं घोरमास्थिताः एवं कष्टमनुप्राप्ता ह्य् अल्पशेषाः प्रजास्ततः //
varṇāśramaparibhraṣṭāḥ saṃkaraṃ ghoramāsthitāḥ evaṃ kaṣṭamanuprāptā hy alpaśeṣāḥ prajāstataḥ //
Having fallen away from the discipline of varṇa and āśrama, the people entered a dreadful state of social mixture and disorder. Thus they came to great suffering, and as a result only a small remnant of the population was left.
It does not describe cosmic pralaya directly; it depicts a social “dissolution” in Kali Yuga—when deviation from varṇāśrama leads to disorder, widespread suffering, and a reduced population.
It implies that rulers and householders must uphold varṇāśrama-based duties (discipline, ethical conduct, proper rites and responsibilities) to prevent varṇa-saṅkara-like disorder and the societal suffering that follows.
No specific Vāstu or temple rule is stated; the ritual takeaway is that abandoning prescribed dharma (including life-stage duties and rites) is portrayed as a root cause of communal decline.