Matsya Purana — Yayāti and His Sons: The Exchange of Youth and Old Age
पूर्णे वर्षसहस्रे तु ते प्रदास्यामि यौवनम् स्वं चादास्यामि भूयो ऽहं पाप्मानं जरया सह //
pūrṇe varṣasahasre tu te pradāsyāmi yauvanam svaṃ cādāsyāmi bhūyo 'haṃ pāpmānaṃ jarayā saha //
When a full thousand years have passed, I shall grant you youth again; and I shall once more take upon myself my sin—together with old age.
It frames the deluge-era episode as a divine covenant: Matsya not only protects Manu through cosmic upheaval but also grants extraordinary longevity and renewal, showing divine governance over time, decay, and karmic burden.
By implying that righteous endurance and obedience to divine instruction are rewarded, it supports the Purāṇic ethic that a ruler/householder should uphold dharma over long spans—trusting that divine order can mitigate suffering and restore strength for continued duty.
No direct Vāstu or temple-architecture rule appears in this verse; its ritual takeaway is the Purāṇic idea of divine removal of pāpa (impurity), which underlies purification themes later expressed through rites, vows, and consecratory practices.