Narada Purana — Purva Bhaga, Shloka 41
Tithi-Nirṇaya for Vratas: Ekādaśī Rules, Saṅkrānti Punya-kāla, Eclipse Observances, and Prāyaścitta
एकादशी कलामात्रा द्वादश्यां तु प्रतीयते । द्वादशी च त्रयोदश्यामस्ति चेत्सा परा स्मृता ॥ ४१ ॥
ekādaśī kalāmātrā dvādaśyāṃ tu pratīyate | dvādaśī ca trayodaśyāmasti cetsā parā smṛtā || 41 ||
Bila Ekādaśī hanya hadir sekejap (kalā-mātra) dan baru tampak pada Dvādaśī, serta Dvādaśī itu berlanjut hingga Trayodaśī, maka Dvādaśī itulah yang diingat sebagai ‘Parā’ (yang unggul/penentu) untuk upacara.
Sanatkumara (in instruction to Narada on vrata and tithi-determination)
Vrata: Ekādaśī (with Dvādaśī-parā determination)
Primary Rasa: shanta
Secondary Rasa: bhakti
FAQs
It safeguards the sanctity of Ekādaśī-vrata by insisting on correct tithi-determination; when Ekādaśī is only momentary and effectively falls on Dvādaśī, the tradition treats the extended Dvādaśī as the decisive ‘Parā’ day for proper observance.
Bhakti is expressed through disciplined vrata; the verse emphasizes that devotion is not merely sentiment but includes careful adherence to dharma—observing the vow on the correctly ascertained lunar day.
Vedāṅga Jyotiṣa (calendar/astronomical reckoning) is implied: recognizing fractional tithi presence (kalā), and deciding observance when Dvādaśī overlaps into Trayodaśī.