Yoga Sūtra Chapter Two verse 38

ब्रह्मचर्य प्रतिष्ठायां वीर्यलाभः ॥३८॥

brahmacarya-pratiṣṭhāyāṃ vīrya-lābhaḥ ||38||

When established in conservation,
vigour is attained.

brahmacarya - continence; conservation; a life stagepratiṣṭha - establishedvīrya - vigourlābha - attained