Matsya Purana — Sādhāraṇa Śrāddha: General Ancestral Rite
युगादयः स्मृता ह्य् एता दत्तस्याक्षय्यकारिकाः तथा मन्वन्तरादौ च देयं श्राद्धं विजानता //
yugādayaḥ smṛtā hy etā dattasyākṣayyakārikāḥ tathā manvantarādau ca deyaṃ śrāddhaṃ vijānatā //
These times—beginning with the yugas—are remembered as conferring imperishable (akṣaya) fruit upon gifts. Likewise, at the commencement of a Manvantara, one who understands should perform the śrāddha rites.
Indirectly, it points to cosmic time cycles (yugas and manvantaras) that frame creation and dissolution; the verse uses these transitions as especially potent times for accruing imperishable religious merit.
It advises the dharmic person—especially the householder responsible for rites—to give charity and perform śrāddha at auspicious cosmic junctures; a king, as guardian of dharma, is also expected to uphold and model such time-based ritual observances.
Ritually, it emphasizes kāla-niyama (the rule of proper timing): gifts and śrāddha performed at yuga-related sacred periods and at a Manvantara’s beginning are said to yield akṣaya (undiminishing) merit.