Matsya Purana — Measures of Time: Caturyuga Computation
ततः समुदिता वर्णास् त्रेतायां धर्मशालिनः क्रियावन्तः प्रजावन्तः समृद्धाः सुखिनश्च वै //
tataḥ samuditā varṇās tretāyāṃ dharmaśālinaḥ kriyāvantaḥ prajāvantaḥ samṛddhāḥ sukhinaśca vai //
Then, in the Tretā-yuga, the social orders (varṇas) became fully established—upholding dharma, devoted to prescribed rites and duties, blessed with progeny, prosperous, and indeed happy.
It does not describe pralaya directly; it characterizes the post-cosmic-order world of the Tretā-yuga, where dharma and social structure are firmly established.
By praising a society that is dharma-centered and kriyā-oriented, the verse implies that rulers should uphold varṇa-based order and that householders should perform prescribed rites, sustain lineage, and support prosperity through righteous conduct.
The key point is ritual: “kriyāvantaḥ” highlights commitment to yajñas, saṃskāras, and prescribed religious duties—an enabling foundation for temple/ritual culture, though no specific Vāstu rule is stated in this verse.