Yoga Sutras of Patanjali · 2.38

ब्रह्मचर्यप्रतिष्ठायां वीर्यलाभः ॥३८॥

brahmacarya-pratiṣṭhāyāṁ vīrya-lābhaḥ

When brahmacarya is established, the yogi gains vigour.

— Yoga Sutras of Patanjali 2.38

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).