Matsya Purana — Sādhāraṇa Śrāddha: General Ancestral Rite
पितॄन् आवाहयिष्यामि कुर्वित्युक्तस्तु तैः पुनः उशन्तस्त्वा तथायन्तु ऋग्भ्याम् आवाहयेत्पितॄन् //
pitṝn āvāhayiṣyāmi kurvityuktastu taiḥ punaḥ uśantastvā tathāyantu ṛgbhyām āvāhayetpitṝn //
When instructed by them, he should again say, “I shall invoke the Pitṛs; I am performing the rite.” Then, reciting the two Ṛk-verses beginning with “uśantaḥ tvā…”, he should invoke the ancestors.
This verse is not about Pralaya; it focuses on Śrāddha ritual protocol—specifically the formal invitation (āvāhana) of the Pitṛs using prescribed Ṛgvedic verses.
It supports gṛhastha-dharma: the householder must perform ancestral rites correctly, verbally declaring the act and invoking the Pitṛs with Vedic authority, reflecting disciplined, rule-based dharma.
The significance is ritual, not architectural: it prescribes the exact liturgical step—invoking the Pitṛs with two specific Ṛk-mantras (beginning “uśantaḥ tvā…”) after a formal declaration.