Yoga Sutras of Patanjali · 2.43

कायेन्द्रियसिद्धिरशुद्धिक्षयात्तपसः ॥४३॥

kāyendriya-siddhir aśuddhi-kṣayāt tapasaḥ

From tapas, with the destruction of impurity, comes perfection of the body and the senses.

— Yoga Sutras of Patanjali 2.43

Source: Sanskrit attributed to Patanjali (c. 2nd century BCE – 4th century CE). Public-domain English readings drawn from Swami Vivekananda's 'Raja Yoga' (1896) and Charles Johnston's 'The Yoga Sutras of Patanjali' (1912).