Matsya Purana — Soma
प्रजावतां प्रसिद्धैषा उक्ता श्राद्धकृतां च वै तेषां निवापे दत्तं हि तत्कुलीनैस्तु बान्धवैः //
prajāvatāṃ prasiddhaiṣā uktā śrāddhakṛtāṃ ca vai teṣāṃ nivāpe dattaṃ hi tatkulīnaistu bāndhavaiḥ //
This practice is well known among those who have descendants and is indeed taught for performers of śrāddha; for them, the nivāpa offering is truly to be given by relatives belonging to that very family line.
This verse is not about pralaya; it focuses on śrāddha-dharma—specifically, who should give the nivāpa offering for ancestors within a family line.
It reinforces gṛhastha-dharma: ancestral rites are a lineage responsibility, and qualified family relatives (bāndhavas of the same kula) should ensure the nivāpa is duly offered during śrāddha.
The ritual significance is the nivāpa in śrāddha—an earmarked offering for the Pitṛs—emphasizing proper agency (performed/given by one’s own kula-relatives) for the rite to be socially and ritually valid.