क्षये वाप्यथवा वृद्धौ संप्राप्ते वा दिनोदये । उपोष्या द्वादशी पुण्या पूर्वविद्धां विवर्जयेत् ॥ २५ ॥
kṣaye vāpyathavā vṛddhau saṃprāpte vā dinodaye | upoṣyā dvādaśī puṇyā pūrvaviddhāṃ vivarjayet || 25 ||
Sama ada tithi itu memendek (kṣaya) atau memanjang (vṛddhi), atau pun bermula ketika terbit matahari, Dvādaśī yang suci hendaklah dipelihara dengan berpuasa; hendaklah dielakkan Dvādaśī yang ‘tertembus’ oleh tithi sebelumnya (pūrvaviddhā).
Narada (teaching tithi-based vrata procedure in the Uttara-Bhaga context)
Vrata: Dvādaśī (connected to Ekādaśī-vrata observance)
Primary Rasa: shanta
Secondary Rasa: bhakti
It emphasizes that correct timing (tithi-śuddhi) is itself a form of dharma: Dvādaśī fasting is sacred, but it should be performed on a properly qualified Dvādaśī, avoiding impurity caused by overlap with the prior tithi (pūrvaviddhā).
By prescribing careful observance of Dvādaśī (closely linked with Vaiṣṇava vrata discipline), it frames bhakti as disciplined worship—devotion expressed through regulated fasting and adherence to scriptural calendrical rules.
Jyotiṣa (Vedāṅga astrology/calendar science): it uses technical tithi conditions like kṣaya (shortened tithi), vṛddhi (extended tithi), sunrise-based determination, and the rule to reject a pūrvaviddhā tithi for vrata decisions.