Matsya Purana — Soma
सोमाच्चैवामृतप्राप्तिः पितॄणां तर्पणं तथा सौम्या बर्हिषदः काव्या अग्निष्वात्तास्तथैव च //
somāccaivāmṛtaprāptiḥ pitṝṇāṃ tarpaṇaṃ tathā saumyā barhiṣadaḥ kāvyā agniṣvāttāstathaiva ca //
From Soma indeed comes the obtaining of amṛta (ambrosia); and likewise the tarpaṇa, the libation offered to the Pitṛs, the Ancestors. The Saumya Pitṛs, the Barhiṣads, the Kāvyas, and likewise the Agniṣvāttas are to be understood in this connection.
It does not address pralaya directly; it teaches ritual cosmology—Soma as a source linked with amṛta and the nourishment/satiation of Pitṛs through tarpaṇa.
It supports the gṛhastha’s obligatory pitṛ-kṛtya: performing tarpaṇa and understanding the ancestral classes (Saumya, Barhiṣad, Kāvya, Agniṣvātta) as part of dharma that sustains lineage and social-religious order.
Ritual significance: it highlights tarpaṇa and the Soma–amṛta principle behind ancestral offerings, and names key Pitṛ categories typically invoked/recognized in śrāddha-related rites.