Sings Bhagavad Gita:
यथा दीपो निवातस्थो नेङ्गते सोपमा स्मृता ।
योगिनो यतचित्तस्य युञ्जतो योगमात्मनः ॥६- १९॥
yathā dīpo nivātastho
ne’ngate so’pamā smṛtā,
yuñjato yogam ātmanaḥ (19)
“An analogy is (usually) drawn between the lamp whose flame does not flicker because there is no wind and the fully restrained mind of a yogi engaged in contemplation of God.”
When a lamp is kept where there is not a whiff of air, its wick burns steadily and the flame goes straight up-it does not tremble. So it is used as a simile for the subdued mind of a yogi who has completely given himself up to God.