Matsya Purana — Code of Conduct and Vow-Procedure for Courtesans
एवं त्रयोदशं यावन् मासमेवं द्विजोत्तमान् तर्पयेत यथाकामं प्रोषिते ऽन्यं समाचरेत् //
evaṃ trayodaśaṃ yāvan māsamevaṃ dvijottamān tarpayeta yathākāmaṃ proṣite 'nyaṃ samācaret //
Thus, for as long as thirteen months, he should—according to his wish and capacity—offer tarpaṇa (water-libations) to the foremost among the twice-born. If the principal person is away on travel, he should perform the rite for another suitable substitute.
This verse does not discuss pralaya; it focuses on dharma in the form of tarpana/ancestral rites and their observance over a prescribed period.
It frames a householder’s (and by extension a ruler’s) obligation to maintain ritual continuity—performing tarpana over a defined cycle and ensuring the rite is still carried out even if the principal person is away by appointing an eligible substitute.
The significance is ritual: it prescribes the duration (up to thirteen months) and the contingency rule (if the intended person is absent, perform it with another qualified participant/recipient) for proper tarpana observance.