Shiva Purana
तत्पुत्रोहं भवेयं चेद्धरिं तं पीडयाम्यहम्॥ इति कृत्वा मतिं भीमस्तपस्तप्तुं महद्ययौ॥ २१॥
If I am the true son of my mother I shall surely harass Viṣṇu. Thinking thus Bhīma went to perform a great penance.
english translation
tatputrohaM bhaveyaM ceddhariM taM pIDayAmyaham॥ iti kRtvA matiM bhImastapastaptuM mahadyayau॥ 21॥
hk transliteration by Sanscript