Mahabharata 1.71.18

ब्रह्मचर्यं चरिष्यामि त्वय्यहं परमं गुरौअनुमन्यस्व मां ब्रह्मन्सहस्रं परिवत्सरान्

brahmacaryaṃ cariṣyāmi tvayyahaṃ paramaṃ gurauanumanyasva māṃ brahmansahasraṃ parivatsarān

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