Matsya Purana — Measures of Time: Caturyuga Computation
इज्या दानं तपः सत्यं त्रेताधर्मास्तु वै स्मृताः तदा प्रवर्तते धर्मो वर्णाश्रमविभागशः मर्यादास्थापनार्थं च दण्डनीतिः प्रवर्तते //
ijyā dānaṃ tapaḥ satyaṃ tretādharmāstu vai smṛtāḥ tadā pravartate dharmo varṇāśramavibhāgaśaḥ maryādāsthāpanārthaṃ ca daṇḍanītiḥ pravartate //
Worship in sacrificial duty (ijyā), charity (dāna), austerity (tapas), and truthfulness (satya) are remembered as the dharmas of the Tretā age. Then dharma proceeds according to the divisions of varṇa and āśrama; and, for the establishment of proper boundaries and order, the science of punishment and governance (daṇḍanīti) also comes into operation.
This verse is not about Pralaya; it outlines how dharma functions in the Tretā-yuga—through worship, charity, austerity, truth, and through structured social order supported by governance (daṇḍanīti).
It implies that when society is organized by varṇa and āśrama, the king must uphold maryādā (lawful limits) through daṇḍanīti—fair discipline and jurisprudence—while householders sustain dharma through sacrifice/worship, charity, austerity, and truth.
Ritually, it emphasizes ijyā (yajña/temple-centered worship) as a core Tretā-yuga duty; it does not directly teach Vāstu rules, but it frames ritual order as something protected by social discipline and statecraft.