This verse is from the Bhagavad Gita, Chapter 6, Verse 19. It is written in Sanskrit and translates to English as follows:
yathā dīpo nivāta-stho neṅgate sopamā smṛitā
yogino yata-chittasya yuñjato yogam ātmanaḥ || 19 ||
"Just as the flame of a lamp placed in a place without wind does not move, similarly the mind of a yogi who is focused on the soul and has control over his mind does not get disturbed."
Lord Krishna teaches here that a yogi has to completely control his senses and mind. The turmoil of the outside world or the storm of thoughts cannot disturb him. This is that state of meditation yoga where a person feels the light inside him and becomes stable in his soul.
Yatha - Like
Deepah - lamp
Nivatastha - situated in a place without wind
Na - Nahi
Ingate - Moving
sopama - such a simile
smriti - considered
yoginah - of a yogi
yatachittasya - whose mind is controlled
yuñjatah - one who is engaged in sadhana
yogam - in yoga, in meditation
atmanah - of the soul, self-control.