Matsya Purana — The Kalyāṇa-Saptamī
सर्वपापहरा नित्यं सर्वदैवतपूजिता सर्वदुष्टोपशमनी सदा कल्याणसप्तमी //
sarvapāpaharā nityaṃ sarvadaivatapūjitā sarvaduṣṭopaśamanī sadā kalyāṇasaptamī //
Kalyāṇa-Saptamī ever removes all sins; it is revered by all the gods; it pacifies every form of wickedness, and is always auspicious.
This verse does not address pralaya; it focuses on ritual time (Saptamī tithi) and its purifying, protective religious merit.
It supports dharma through vrata-observance: a householder (and a king as public exemplar) upholds social and personal purity by honoring auspicious tithis believed to remove sin and restrain harmful tendencies.
Ritually, it praises Kalyāṇa-Saptamī as a powerful observance day; no specific Vāstu or temple-construction rule is stated in this verse.