Matsya Purana — Glory of Tīrtha-Śrāddha: Best Times
विष्णोर् देहसमुद्भूताः कुशाः कृष्णास्तिलास्तथा श्राद्धस्य रक्षणायालम् एतत्प्राहुर्दिवौकसः //
viṣṇor dehasamudbhūtāḥ kuśāḥ kṛṣṇāstilāstathā śrāddhasya rakṣaṇāyālam etatprāhurdivaukasaḥ //
The kuśa grass and the black sesame seeds are said to have arisen from the body of Viṣṇu; the gods declare that these are fully sufficient for the protection of the Śrāddha rite.
It does not describe Pralaya directly; it instead grounds ritual materials (kuśa and black sesame) in a divine origin from Viṣṇu, emphasizing sacred protection rather than cosmic dissolution.
It supports the gṛhastha duty of performing Śrāddha correctly: using kuśa and black sesame is presented as a dharmic safeguard, ensuring the rite’s sanctity and efficacy for ancestors.
Ritually, it identifies kuśa and black sesame as key protective substances in Śrāddha—purifying, warding off obstacles, and securing the intended merit of the ancestral offering.