Matsya Purana — The Greatness of Prayāga
दाता वै लभते भोगान् गां च यत्कर्मणः फलम् तानि कर्माणि पृच्छामि पुनस्तैः प्राप्यते मही //
dātā vai labhate bhogān gāṃ ca yatkarmaṇaḥ phalam tāni karmāṇi pṛcchāmi punastaiḥ prāpyate mahī //
Indeed, the giver attains enjoyments and also cattle—the fruit corresponding to his deed. I ask again about those very acts: by which of them is the earth (land/kingdom) obtained?
This verse does not address Pralaya directly; it focuses on karmic causality (karmaphala), stating that giving yields specific worldly results like enjoyments and cattle.
It frames charity as a practical pillar of dharma: the householder/king who gives gains prosperity (bhoga, cattle), and Manu specifically seeks which righteous acts can even lead to obtaining land or sovereignty—linking dāna to rajadharma and social stability.
No Vastu or temple-building rule is stated here; the ritual significance is general—dāna (charitable gifting) is treated as a dharmic act with measurable fruits, motivating prescribed rites of giving.