Matsya Purana — The Kalyāṇa-Saptamī
*ईश्वर उवाच सौरं धर्मं प्रवक्ष्यामि नाम्ना कल्याणसप्तमीम् विशोकसप्तमीं तद्वत् फलाढ्यां पापनाशिनीम् //
*īśvara uvāca sauraṃ dharmaṃ pravakṣyāmi nāmnā kalyāṇasaptamīm viśokasaptamīṃ tadvat phalāḍhyāṃ pāpanāśinīm //
The Lord said: “I shall expound the Sun-related religious observance, named ‘Kalyāṇa-saptamī’, also called ‘Viśoka-saptamī’—rich in merit and a destroyer of sins.”
This verse does not address pralaya; it introduces a Sun-related vow (saptamī-vrata) aimed at removing sin and sorrow.
It frames a practical dharma for lay life: a householder (and by extension a king as public exemplar) should observe meritorious vows—here, a Saura saptamī—seeking ethical purification (pāpa-nāśana) and well-being (kalyāṇa/viśoka).
The ritual significance is explicit: it announces a specific vrata centered on Sūrya and the saptamī tithi; architectural rules are not mentioned in this verse.