Mahabharata 15.35.14
तपोबलव्ययं कृत्वा सुमहच्चिरसंभृतम्माण्डव्येनर्षिणा धर्मो ह्यभिभूतः सनातनः
tapobalavyayaṃ kṛtvā sumahaccirasaṃbhṛtammāṇḍavyenarṣiṇā dharmo hyabhibhūtaḥ sanātanaḥ
Our plain-language meaning of this verse is waiting for scholar review.
Open in the book