Matsya Purana — Ekoddiṣṭa Śrāddha
शूद्रेषु मासमाशौचं सपिण्डेषु विधीयते नैशं वाकृतचूडस्य त्रिरात्रं परतः स्मृतम् //
śūdreṣu māsamāśaucaṃ sapiṇḍeṣu vidhīyate naiśaṃ vākṛtacūḍasya trirātraṃ parataḥ smṛtam //
For a Śūdra, āśauca is prescribed for a month, and the same is enjoined among sapinda (blood-related kin). But for one who has not yet undergone the cūḍā hair-rite (first tonsure), impurity is held to last only three nights thereafter.
This verse is not about Pralaya; it belongs to the Matsya Purana’s dharma section and lays down practical rules of ritual impurity (āśauca) connected with death/birth and kinship obligations.
It guides householders (and rulers overseeing social order) on how long mourning-impurity applies in different cases—especially for Śūdras and for sapinda relatives—so that daily rites, temple access, and śrāddha-related duties are timed correctly.
The significance is ritual rather than architectural: it specifies āśauca durations that determine when one may resume rites such as śrāddha, offerings, and other purity-dependent ceremonies.