Bhagavad Gita 6.19

The wise man who has conquered his mind and is absorbed in the Self is like a lamp that does not flicker, as it stands sheltered from every wind.

यथा दीपो निवातस्थो नेङ्गते सोपमा स्मृता।
योगिनो यतचित्तस्य युञ्जतो योगमात्मनः॥

yathā dīpo nivātastho neṅgate sopamā smṛtā|
yogino yatacittasya yuñjato yogamātmanaḥ||

English translation (above): Shri Purohit Swami (1935), public domain. Sanskrit text via github.com/gita/gita (Unlicense).