Matsya Purana — The Kalyāṇa-Saptamī
ततस्त्रयोदशे मासि गा वै दद्यात्त्रयोदश वस्त्रालंकारसंयुक्ताः सुवर्णास्याः पयस्विनीः //
tatastrayodaśe māsi gā vai dadyāttrayodaśa vastrālaṃkārasaṃyuktāḥ suvarṇāsyāḥ payasvinīḥ //
Then, in the thirteenth month, one should indeed give thirteen cows—each adorned with garments and ornaments—milch cows whose faces are decorated with gold.
This verse does not address pralaya; it prescribes a dāna (charitable) rite—specifically the gifting of thirteen ornamented milch cows in a timed observance.
It presents a householder/royal duty of dāna-dharma: structured giving at a specified time, emphasizing generosity with valuable, life-sustaining gifts (milch cows) enhanced by respectful adornment.
The ritual significance is the prescribed form of go-dāna: the number (thirteen), the timing (thirteenth month), and the proper presentation (cows with garments, ornaments, and gold facial decoration).