Bhagwad Gita
Chapter 6, Verse 19
यथा दीपो निवातस्थो नेङ्गते सोपमा स्मृता।
योगिनो यतचित्तस्य युञ्जतो योगमात्मनः।।6.19।।
As a lamp in a windless place does not waver, so the transcendentalist, whose mind is controlled, remains always steady in his meditation on the transcendent Self.