Shiva Purana
मुनयस्सत्यनिरतास्तपस्तप्त्वा सुदुश्चरम् ॥ सत्यधर्मरतास्सिद्धास्ततस्स्वर्गं च ते गताः ॥ ३२॥
After performing very difficult penance, it is by depending solely on Truth, by maintaining truthful virtue that the sages have attained Siddhis and reached heaven.
english translation
munayassatyaniratAstapastaptvA suduzcaram ॥ satyadharmaratAssiddhAstatassvargaM ca te gatAH ॥ 32॥
hk transliteration by Sanscript