Matsya Purana — Ekoddiṣṭa Śrāddha
चतुर्थस्य पुनः कार्यं न कदाचिदतो भवेत् ततः पितृत्वमापन्नः सर्वतस्तुष्टिमागतः //
caturthasya punaḥ kāryaṃ na kadācidato bhavet tataḥ pitṛtvamāpannaḥ sarvatastuṣṭimāgataḥ //
But thereafter, no further obligation remains for the fourth; then, having attained the status of a pitṛ (venerable ancestor), he becomes satisfied in every respect.
This verse is not about pralaya; it focuses on dharma—specifically the completion of an obligation that culminates in the attainment of pitṛ-status and resulting satisfaction.
It implies a graded set of obligations (often read as stages/roles within dharma); once the prescribed duty for the ‘fourth’ is fulfilled, no extra burden remains, and the person is regarded as having fulfilled fatherly/ancestral responsibility—an ideal relevant to householders and, by extension, rulers as exemplars of dharma.
The significance is ritual-ethical rather than architectural: it emphasizes completion of prescribed rites/duties connected with pitṛ-satisfaction (commonly associated with śrāddha/tarpaṇa frameworks), after which the obligation is considered concluded.