Bhagavad Gītā Chapter Six verse 19

यथा दीपो निवातस्थो नेङ्गते सोपमा स्मृता ।
योगिनो यतचित्तस्य युञ्जतो योगमात्मन: ॥

yathā dīpo nivāta-stho na-iṅgate sa-upamā smṛtā |
yogino yata-cittasya yuñjato yogam ātmanaḥ ||

yathā - according asdīpa - light, lamp, lanternnivāta - sheltered from the wind, calm; asylum, refugestha - standing, staying, abiding, being situated in; existing, or being in, or on, or amongiṅg - to move, agitate, shake; waverupamā - comparison, resemblance, equality, similaritysmṛti - remembrance; memory; mindfulness; the whole body of sacred tradition or what is remembered by human teachers and constantly revisedyogin - a follower of the yoga systemyata - restrained, held in, held forth, kept down or limited, subdued, governed, controlledcitta - psyche (the totality of the human mind, conscious and unconscious); mind; heartyuñjāna - the act of uniting, joining, arranging, performing, yoking, fixingyoga - the act of yoking, joining, attaching, harnessing; a yoke, team, vehicle, conveyance; employment, use, application, performance; a means, expedient, device, way, manner, methodātman - essence; the highest personal principle of life; the individual soul, self

Commentaries and Reflections

Commentary by T Krishnamacharya:

Ekāgratā is compared to the sharp tip
of the steady flame of a Ghee Lamp
when not exposed to any wind.
In other words,
the mind should not move
anywhere else other than in the
direction fixed for Dhāraṇā.
Obviously the Viṣaya for Dhāraṇā
and Dhyānam should be the same.
The stronger the Dhāraṇā,
the steadier the Dhyānam.”