Matsya Purana — Omens in Tripura and the Nārada–Maya Dialogue on Dharma
स इष्टप्रापको धर्म आचार्यैरुपदिश्यते इतरश्चानिष्टफल आचार्यैर्नोपदिश्यते //
sa iṣṭaprāpako dharma ācāryairupadiśyate itaraścāniṣṭaphala ācāryairnopadiśyate //
That dharma which leads to the attainment of the desired goal is taught by the teachers; but that other course, which yields undesirable results, is not taught by the teachers.
This verse does not describe pralaya directly; it frames dharma pragmatically—true dharma is what leads to wholesome, desired outcomes, while harmful-result paths are not sanctioned by authoritative teachers.
It gives a rule of discernment: a king or householder should follow conduct endorsed by competent ācāryas because it yields iṣṭa (welfare, stability, merit), and avoid actions that predictably produce aniṣṭa (social harm, personal downfall, demerit).
No specific vastu or temple rule is stated; however, it supports the broader Matsya Purana principle that rituals and procedures are valid when transmitted by qualified teachers and when they produce auspicious, intended results.