Mahabharata 14.50.17

यद्दुरापं दुराम्नायं दुराधर्षं दुरन्वयम्तत्सर्वं तपसा साध्यं तपो हि दुरतिक्रमम्

yaddurāpaṃ durāmnāyaṃ durādharṣaṃ duranvayamtatsarvaṃ tapasā sādhyaṃ tapo hi duratikramam

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