Matsya Purana — Cosmography of Śākadvīpa and Successive Dvīpas: Mountains
न तेषु संकरः कश्चिद् वर्णाश्रमकृतः क्वचित् धर्मस्य चाव्यभीचाराद् एकान्तसुखिनः प्रजाः //
na teṣu saṃkaraḥ kaścid varṇāśramakṛtaḥ kvacit dharmasya cāvyabhīcārād ekāntasukhinaḥ prajāḥ //
Among them there was never any confusion of social and spiritual duties arising from varṇa and āśrama; and because dharma was never violated, the people lived in undisturbed, single-minded happiness.
This verse is not about pralaya; it describes stable societal order—when dharma is not transgressed, the populace remains secure and content, implying the opposite of the disorder associated with decline.
It reflects rajadharma: a king should uphold dharma so that varṇa-āśrama responsibilities function without conflict. For householders, it stresses steady, non-deviating practice of one’s prescribed duties as the basis of social harmony and personal well-being.
No specific vastu/temple rule is stated; the ritual takeaway is the principle of avyabhicāra—consistent, non-deviating observance of dharma—which underlies the efficacy and stability of all rites and institutions.