Matsya Purana — Soma
यस्मात्तामनुमन्यन्ते पितरो दैवतैः सह तस्मादनुमतिर्नाम पूर्णत्वात्पूर्णिमा स्मृता //
yasmāttāmanumanyante pitaro daivataiḥ saha tasmādanumatirnāma pūrṇatvātpūrṇimā smṛtā //
Because the Pitṛs (ancestors), together with the gods, grant their assent to that tithi, it is therefore called Anumati; and because it is the state of fullness, it is remembered as Pūrṇimā (the Full Moon).
This verse is not about Pralaya; it explains sacred lunar timekeeping—why the full-moon tithi is called Anumati and Pūrṇimā—framing ritual time as divinely and ancestrally sanctioned.
It supports dharmic duty by emphasizing correct ritual timing: householders (and rulers setting public observances) should honor Pūrṇimā as a day favored by both Devas and Pitṛs, making it suitable for worship, offerings, and ancestral rites.
Ritually, it identifies Pūrṇimā as a fully potent tithi (pūrṇatva) and “Anumati” (divine/ancestral consent), implying it is an auspicious time for puja, vrata observance, and Pitṛ-related offerings rather than a Vāstu/temple-measurement rule.