Matsya Purana — Measures of Time: Caturyuga Computation
शुभाः प्रकृतयस्तेषां धर्मा वर्णाश्रमाश्रयाः संकल्पितेन मनसा वाचा वा हस्तकर्मणा त्रेतायुगे ह्यविकले कर्मारम्भः प्रसिध्यति //
śubhāḥ prakṛtayasteṣāṃ dharmā varṇāśramāśrayāḥ saṃkalpitena manasā vācā vā hastakarmaṇā tretāyuge hyavikale karmārambhaḥ prasidhyati //
Their dispositions are auspicious, and their duties rest upon the disciplines of varṇa and āśrama. In the Tretā-yuga, when it is still uncorrupted, the undertaking of action becomes effective—whether through an intention formed in the mind, through speech, or through deeds performed by the hand.
This verse does not discuss Pralaya directly; it explains yuga-specific dharma, emphasizing that in the (unimpaired) Tretā-yuga actions succeed readily even when initiated by intention, speech, or physical effort.
It frames duty as varṇāśrama-based discipline and highlights accountability across mind, speech, and deed—guiding rulers and householders to cultivate pure intention, truthful speech, and righteous action, especially when initiating any undertaking.
No explicit Vāstu or temple rule is stated; the relevant takeaway for ritual/works is that successful performance begins with saṃkalpa (resolve), then proper verbal formulation (mantra/command), and finally correct manual execution.