Matsya Purana — The Greatness of Prayāga
अश्रद्दधानो ह्यशुचिर् दुर्मतिस्त्यक्तमङ्गलः एते पातकिनः सर्वे तेनेदं भाषितं त्वया //
aśraddadhāno hyaśucir durmatistyaktamaṅgalaḥ ete pātakinaḥ sarve tenedaṃ bhāṣitaṃ tvayā //
Indeed, one who is faithless is impure, ill-minded, and has abandoned auspicious conduct—such people are all sinners; it is with reference to them that this has been spoken by you.
This verse is not about Pralaya; it classifies moral and ritual defects (faithlessness, impurity, wrong-mindedness) as marks of sinful persons, within an ethical teaching context.
It implies that rulers and householders must cultivate śraddhā (reverent faith), maintain śauca (purity), and uphold maṅgala (auspicious, dharmic conduct); those who reject these become unfit for right counsel and righteous living.
Indirectly ritual: the verse stresses maṅgala and śauca—core prerequisites for rites (pujā, dāna, śrāddha). It does not give Vāstu or temple-building rules, but it frames the moral-ritual eligibility required before such acts.