Matsya Purana — The Greatness of Prayāga
*मार्कण्डेय उवाच अश्रद्धेयं न वक्तव्यं प्रत्यक्षमपि यद्भवेत् नरस्याश्रद्दधानस्य पापोपहतचेतसः //
*mārkaṇḍeya uvāca aśraddheyaṃ na vaktavyaṃ pratyakṣamapi yadbhavet narasyāśraddadhānasya pāpopahatacetasaḥ //
Mārkaṇḍeya said: “One should not speak of a matter that will not be believed—even if it is directly evident—when addressing a man who lacks faith, whose mind has been struck and clouded by sin.”
This verse is not about Pralaya; it teaches nīti (ethical counsel): spiritual or factual truths should not be pressed upon a listener who is incapable of trust due to a sin-clouded mind.
It frames a practical rule of counsel: a king, minister, or householder should judge the recipient’s receptivity and integrity; advice—even true and evident—fails when given to the faithless, and can waste effort or provoke harm.
No direct Vāstu/ritual procedure is stated; indirectly, it implies that sacred instructions (including ritual and temple norms) should be taught only to qualified, receptive persons.