Bhagavad Gita Chapter 6.19
yathā dīpo nivāta-stho
neńgate sopamā smṛtā
yogino yata-cittasya
yuñjato yogam ātmanaḥ
Translation
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.