Chapter 6 · verse 19 · gita.yoga.org

Bhagavad Gita 6.19

यथा दीपो निवातस्थो नेङ्गते सोपमा स्मृता। योगिनो यतचित्तस्य युञ्जतो योगमात्मनः

As a lamp placed in a windless spot does not flicker, so is the Yogi of a controlled mind, who practices Yoga in the Self, compared.