B.G 6.19

यथा दीपो निवातस्थो नेङ्गते सोपमा स्मृता। योगिनो यतचित्तस्य युञ्जतो योगमात्मनः ॥१९॥

yathā dīpo nivātastho neṅgate sopamā smr̥tā। yogino yatacittasya yuñjato yogamātmanaḥ ॥19॥

[यथा दीपो निवातस्थो न इङ्गते स उपमा स्मृता। योगिनो यत चित्तस्य युञ्जतो योगम् आत्मनः॥
यथा (yathā) - as; दीपः (dīpaḥ) - lamp; निवातस्थः (nivātasthaḥ) - in a windless place; न (na) - does not; इङ्गते (iṅgate) - flicker; स (sa) - that; उपमा (upamā) - analogy; स्मृता (smṛtā) - is considered; योगिनः (yoginaḥ) - of the yogi; यत् (yat) - whose; चित्तस्य (chittasya) - mind; युञ्जतः (yuñjataḥ) - engaged in; योगम् (yogam) - yoga; आत्मनः (ātmanaḥ) - concerning the divine Lord.]

Just as a lamp in a windless place does not flicker, such is the analogy to be considered for a Yogi whose mind is engaged in the Yoga concerning the divine Lord.

Gīta Bhāshya 6.19

'ātmanaḥ yogaṁ' - Yoga concerning the divine Lord

आत्मनः योगं भगवद्विषयं योगम् ॥१९॥

ātmanaḥ yogaṁ bhagavadviṣayaṁ yogam ॥19॥

[आत्मनः योगं (ātmanaḥ yogaṁ) - The expression 'ātmanaḥ yogaṁ' refers to; भगवद्विषयं (bhagavadviṣayaṁ) - concerning the divine Lord; योगम् (yogam) - yoga.]

The expression 'ātmanaḥ yogaṁ' refers to 'Yoga concerning the divine Lord'.