Matsya Purana — The Greatness and Procedure of the Aṅgāra
साधु साध्विति तेनोक्तम् अहो माहात्म्यमुत्तमम् पश्यतो ऽपि भवेद्रूपम् ऐश्वर्यं किमु कुर्वतः //
sādhu sādhviti tenoktam aho māhātmyamuttamam paśyato 'pi bhavedrūpam aiśvaryaṃ kimu kurvataḥ //
“Excellent, excellent!”—so he exclaimed: “Ah, what supreme greatness is this!” Even by merely beholding it, beauty of form and lordly prosperity arise—how much more for one who truly performs it?
This verse does not describe pralaya directly; it teaches a general Purāṇic principle of spiritual efficacy—mere darśana (beholding) can confer visible benefits, and actual performance yields greater fruit.
It encourages active dharmic practice: a king or householder should not rely only on witnessing sacred acts but should sponsor, perform, and uphold them—since doing (kuru) is said to grant even greater prosperity and excellence than merely seeing.
No specific Vāstu rule is named, but the verse supports a common ritual-architectural idea: darśana of a sacred object/rite (such as a deity image, temple, or consecration) is beneficial, while commissioning or performing the rite is even more meritorious.