Mahabharata 12.155.5

यद्दुरापं दुराम्नायं दुराधर्षं दुरुत्सहम्सर्वं तत्तपसा शक्यं तपो हि दुरतिक्रमम्

yaddurāpaṃ durāmnāyaṃ durādharṣaṃ durutsahamsarvaṃ tattapasā śakyaṃ tapo hi duratikramam

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