BhG 6.19

syntax

yathā (as) nivāta-sthaḥ (situated iin a windless place) dīpaḥ (a lamp) na iṅgate (it does not flicker),
[tathā] (so) ātmanaḥ (of the self) yogam yuñjataḥ (of one engaging in yoga) yata-cittasya (of one who restrained the mind) yoginaḥ (of a yogī).
sā upamā (that comparison) smṛtā (it is given).

grammar

yathā	–	av. – as (correlative of: tathā);
dīpaḥ	–	dīpa 1n.1 m. – a lamp (from: √dīp – to blaze, to shine);
nivāta-sthaḥ	–	nivāta-stha 1n.1 m.; yo nivāte tiṣṭhati saḥ – which is situated in a windless place (from: ni = niḥ – out of, away from, without; √vā – to blow, PP ni-vāta – windless; √sthā – to stand, stha – suffix: being in);
na	–	av. – not;
iṅgate	–	√iṅg (to flicker) Praes. Ā 1v.1 – it flickers;
sā	–	tat sn. 1n.1 f. – that;
upamā	–	upamā 1n.1 f. – comparison, similarity (from: upa-√mā – to measure, to compare);
smṛtā	–	smṛtā (√smṛ – to think, to remember) PP 1n.1 f. – remembered, preserved [in tradition];
yoginaḥ	–	yogin 6n.1 m. – of a yogī, of engaged (√yuj – to yoke, to join, to engage, yoga – yoga, yoking, application, a means, one of the schools of Hindu philosophy);
yata-cittasya	–	yata-citta 6n.1 m.; BV: yasya cittaṁ yato ‘sti tasya – of one whose mind is restrained (from: √yam – to hold back, to restrain, PP yata – held back, restrained; √cit – to perceive, to think, PP citta – thought; a thought, mind, heart, consciousness);
yuñjataḥ	–	yuñjant (√yuj – to yoke, to join, to engage) PPr 6n.1 – of one engaging;
yogam	–	yoga 2n.1 m. – yoga, yoking, application, a means, one of the schools of Hindu philosophy (from:√yuj – to yoke, to join, to engage);
ātmanaḥ	–	ātman 6n.1 m. – of the self;

textual variants

yathā → yadā (when);
yata-cittasya → jita-cittasya (whose mind is conquered);
yuñjato → yuṁjate (in one engaged);
ātmanaḥ → ātmani (in the self);

Śāṃkara

tasya yoginaḥ samāhitaṃ yat cittaṃ tasyopamocyate—

yathā dīpaḥ pradīpo nivāta-stho nivāte vāta-varjite deśe sthito neṅgate na calati, sopamā upamīyate’nayety upamā yogajñaiś citta-pracāra-darśibhiḥ smṛtā cintitā yogino yata-cittasya saṃyatāntaḥ-karaṇasya yuñjato yogam anutiṣṭhata ātmanaḥ samādhim anutiṣṭhata ity arthaḥ

Rāmānuja

nivātastho dīpo yathā neṅgate na calati; acalas saprabhas tiṣṭhati; yatacittasya nivṛttasakaletaramanovṛtteḥ yoginaḥ ātmani yogaṃ yuñjataḥ ātmasvarūpasya sopamā; nivātasthatayā niścalasaprabhadīpavan nivṛttasakalamanovṛttitayā niścalo jñānaprabha ātmā tiṣṭhaītyarthaḥ

Śrīdhara

ātmaikyākāratayāvasthitasya cittasyopamānam āha yatheti | vāta-śūnye deśe sthito dīpo yathā neṅgate na vicalati | sopamā dṛṣṭāntaḥ | kasya ? ātma-viṣayaṃ yogaṃ yuñjato ‚bhyasyato yoginaḥ | yataṃ niyataṃ cittaṃ yasya tasya niṣkampatayā prakāśakatayā cācañcalaṃ tac cittaṃ tadvat tiṣṭhatīty arthaḥ

Madhusūdana

samādhau nivṛttikasya cittasyopamānam āha yatheti | dīpa-calana-hetunā vātena rahite deśe sthito dīpo yathā calana-hetv-abhāvān neṅgate na calati, sopamā smṛtā sa dṛṣṭāntaś cintito yogajñaiḥ | kasya ? yogina ekāgra-bhūmau samprajñāta-samādhi-mato ‚bhyāsa-pāṭavād yata-cittasya niruddha-sarva-citta-vṛtter asamprajñāta-samādhi-rūpaṃ yogaṃ nirodha-bhūmau yuñjato ‚nutiṣṭhato ya ātmāntaḥkaraṇaṃ tasya niścalatayā sattvodrekeṇa prakāśakatayā ca niścalo dīpo dṛṣṭānta ity arthaḥ|

ātmano yogaṃ yuñjata iti vyākhyāne dārṣṭāntikālābhaḥ sarvāvasthasyāpi cittasya sarvadātmākāratayātma-pada-vaiyarthyaṃ ca | na hi yogenātmākāratā cittasya sampādyate, kintu svata evātmākārasya sato ‚nātmākāratā nivartyata iti | tasmād dārṣṭāntika-pratipādanārtham evātma-padam | yata-cittasyeti bhāva-paro nirdeśaḥ karma-dhārayo vā yatasya cittasyety arthaḥ

Viśvanātha

nivāta-stho nirvāta-deśa-sthito dīpo neṅgate na calati yaḥ sa eva dīpa upamā yathā yathāvad ity arthaḥ | so ‚ci lope cet pāda-pūraṇam [Pāṇ 6.1.134] iti sandhiḥ | kasyopamā ity ata āha yogina iti

Baladeva

tadā yogī kīdṛśo bhavatīty apekṣāyām āha yatheti | nirvāta-deśa-stho dīpo neṅgate na calati niścalaḥ sa-prabhas tiṣṭhati sa dīpo yathā yathāvad upamā yogajñaiḥ smṛtā cintitā | sopamety atra so ‚ci lope cet pāda-pūraṇam [Pāṇ 6.1.134] iti sūtrāt sandhiḥ | upamā-śabdenopamānaṃ bodhyam | kasyety āha yogina iti | yata-cittasya niruddha-sarva-citta-vṛtter ātmano yogaṃ dhyānaṃ yuñjato ‚nutiṣṭhataḥ | nivṛtta-sakaletara-citta-vṛttir abhyudita-jñāna-yogī niścala-sa-pradīpa-sadṛśo bhavatīti