Matsya Purana — Yuga Durations
त्रेतायां विकृतिं यान्ति वर्णास्त्वेते न संशयः चातुर्वर्ण्यस्य वैकृत्याद् यान्ति दौर्बल्यमाश्रमाः //
tretāyāṃ vikṛtiṃ yānti varṇāstvete na saṃśayaḥ cāturvarṇyasya vaikṛtyād yānti daurbalyamāśramāḥ //
In the Tretā Yuga, these social classes (varṇas) indeed fall into distortion—there is no doubt. And because the fourfold social order becomes corrupted, the stages of life (āśramas) also lapse into weakness and decline.
This verse is not about cosmic dissolution (pralaya); it describes moral and institutional decline within time (yuga), specifically the weakening of varṇa and āśrama structures in the Tretā Yuga.
It implies that when the varṇa framework is corrupted, āśrama duties also weaken; therefore a king should protect dharma through fair governance and discipline, and householders should uphold their prescribed duties so society does not lose strength.
No direct Vāstu or temple-architecture rule is stated here; the takeaway is indirect—ritual life and social institutions lose efficacy when dharma (varna–āśrama order) is distorted.