Mahabharata 3.107.13

स तु तत्र नरश्रेष्ठस्तपो घोरं समाश्रितःफलमूलाम्बुभक्षोऽभूत्सहस्रं परिवत्सरान्

sa tu tatra naraśreṣṭhastapo ghoraṃ samāśritaḥphalamūlāmbubhakṣo'bhūtsahasraṃ parivatsarān

Our plain-language meaning of this verse is waiting for scholar review.