Mahabharata 13.110.84
पूर्णेऽथ दिवसे विंशे यो भुङ्क्ते ह्येकभोजनम्सदा द्वादश मासांस्तु सत्यवादी धृतव्रतः
pūrṇe'tha divase viṃśe yo bhuṅkte hyekabhojanamsadā dvādaśa māsāṃstu satyavādī dhṛtavrataḥ
Our plain-language meaning of this verse is waiting for scholar review.
Open in the book