Matsya Purana — The Rite of the Vibhūti-Dvādaśī Vow
कार्त्तिके चैत्रवैशाखे मार्गशीर्षे च फाल्गुने आषाढे वा दशम्यां तु शुक्लायां लघुभुङ्नरः कृत्वा सायन्तनीं संध्यां गृह्णीयान्नियमं बुधः //
kārttike caitravaiśākhe mārgaśīrṣe ca phālgune āṣāḍhe vā daśamyāṃ tu śuklāyāṃ laghubhuṅnaraḥ kṛtvā sāyantanīṃ saṃdhyāṃ gṛhṇīyānniyamaṃ budhaḥ //
In the months of Kārttika, Caitra, Vaiśākha, Mārgaśīrṣa, Phālguna, or Āṣāḍha—on the bright-fortnight tenth day (Śukla Daśamī)—a man who eats lightly, having performed the evening Sandhyā, should wisely undertake the prescribed niyama, the rule of religious observance.
This verse is not about Pralaya; it prescribes a dharma-practice: observing a niyama on Śukla Daśamī in certain months after performing the evening Sandhyā, with light eating.
It supports the householder’s (and by extension a king’s) duty of disciplined daily worship: perform sāyantana-sandhyā properly and keep regulated observances (niyama) on specified tithis, accompanied by moderation in food (laghubhojana).
The significance is ritual, not architectural: it highlights Sandhyā (twilight worship) and the timing of vrata/niyama on Śukla Daśamī across specific lunar months—useful for Panchāṅga-based observance planning.