BhG 15.6

syntax

yat [padam] (that abode to which) gatvā (after going)
[te] (they) na nivartante (they do not return),
sūryaḥ (Sun) tat [padam] (that abode) na bhāsayate (it does not illuminate),
śaśāṅkaḥ (Moon) [tat padam] (that abode) na [bhāsayate] (it does not illuminate),
pāvakaḥ (fire) [tat padam] (that abode) na [bhāsayate] (it does not illuminate),
tat (that) mama (my) paramam dhāma (the supreme abode) [asti] (it is).

grammar

na	–	av. – not;
tat	–	tat sn. 2n.1 n. – that;
bhāsayate	–	√bhās (to shine, to be bright) caus. Praes. Ā 1v.1 – it causes to shine, it illuminates;
sūryaḥ	–	sūrya 1n.1 m. – Sun;
na	–	av. – not;
śaśāṅkaḥ	–	śaśa-aṅka 1n.1 m.; BV: yasyāṅkaḥ śaśo ‘sti saḥ – rabbit-marked, Moon (from: śaśa – rabbit, hare; aṅka – sign, line, mark);
na	–	av. – not;
pāvakaḥ	–	pāvaka 1n.1 m. – pure, fire (from: √pū – to purify);
yat	–	yat sn. 2n.1 n. – which;
gatvā	–	√gam (to go) absol. – after going;
na	–	av. – not;
nivartante	–	ni-√vṛt (to stop, to turn back) Praes. Ā 1v.3 – they return;
tat	–	tat sn. 1n.1 n. – that;
dhāma	–	dhāman 1n.1 n. – abode, house, state, majesty, splendour (from: √dhā – to put);
paramam	–	parama 1n.1 n. – supreme, the highest (superlative of: para – beyond, ancient, final, the best, the supreme);
mama	–	asmat sn. 6n.1 – my;

textual variants

na tad → na yad (whoich not);
na śaśāṅko na pāvakaḥ → na śaśī na ca pāvakaḥ (not the Moon nor fire);
nivartante → nivarteta (he would return);

The third and fourth pada of verse 15.6 ar similar to the third and fourth pada of verse BhG 8.21;

Śāṃkara

tad eva padaṃ punar viśeṣyate—
tat dhāmeti vyavahitena dhāmnā saṃbadhyate | tad dhāma tejo-rūpaṃ padaṃ na bhāsayate sūrya ādityaḥ sarvāvabhāsana-śaktimattve’pi sati | tathā na śaśāṅkaś candraḥ, na pāvako nāgnir api | yad dhāma vaiṣṇavaṃ padaṃ gatvā prāpya na nivartante, yac ca sūryādir na bhāsayate, tad dhāma padaṃ paramaṃ viṣṇor mama padam

Rāmānuja

tad atmajyotir na sūryo bhāsayate, na śaśāṅkaḥ, na pāvakaś ca / jñānam eva hi sarvasya prakāśakam; bāhyāni tu jyotīṃṣi viṣayendriyasaṃbandhavirodhitamonirasanadvāreṇopakārakāṇi / asya ca prakāśako yogaḥ / tadvirodhi cānādikarma / tannivartanaṃ coktaṃ bhagavatprapattimūlam asaṅgādi / yad gatvā punar na nivartante, tat paramaṃ dhāma paraṃ jyotiḥ mama madīyam; madvibhūtibhūtaḥ mamāṃśa ityarthaḥ / ādityādīnām api prakāśakatvena tasya paramatvam / ādityādīni hi jyotīṃṣi na jñānajyotiṣaḥ prakāśakāni; jñānam eva sarvasya prakāśakam

Śrīdhara

tad eva gantavyaṃ padaṃ viśinaṣṭi na tad iti | tat padaṃ sūryādayo na prakāśayanti | yat prāpya na nivartante yoginaḥ | tad dhāma svarūpaṃ paramaṃ mama | anena sūryādi-prakāśa-viṣayatvena jaḍatva-śītoṣṇādi-doṣa-prasaṅgo nirastaḥ

Madhusūdana

tad eva gantavyaṃ padaṃ viśinaṣṭi na tad iti | yad vaiṣṇavaṃ padaṃ gatvā yogino na nivartante tat padaṃ sarvāvabhāsana-śaktimān api sūryo na bhāsayate | sūryāsta-maye ‚pi candro bhāsako dṛṣṭa ity āśaṅkyāha na śaśāṅkaḥ | sūryācandramasor ubhayor apy asta-maye ‚gniḥ prakāśako dṛṣṭa ity āśaṅkyāha na pāvakaḥ | bhāsayata ity ubhayatrāpy anuṣajyate | kutaḥ sūryādīnāṃ tatra prakāśanāsāmarthyam ity ata āha tad dhāma jyotiḥ svayaṃ-prakāśam ādiyādi-sakala-jaḍa-jyotir-avabhāsakaṃ paramaṃ prakṛṣṭaṃ mama viṣṇoḥ svarūpātmakaṃ padam | na hi yo yad-bhāsyaḥ sa svabhāsakaṃ taṃ bhāsayitum īṣṭe | tathā ca śrutiḥ –
na tatra sūryo bhāti na candra-tārakaṃ
nemā vidyuto bhānti kuto ‚yam agniḥ |
tam eva bhāntam anubhāti sarvaṃ
tasya bhāsā sarvam idaṃ vibhāti || [KaṭhU 2.2.15] iti |
etena tat padaṃ vedyaṃ na vā, ādye vedya-bhinna-veditṛ-sāpekṣatvena dvaitāpattir dvitīye sva-puruṣārthatvāpattir ity apāstam | avedyatve saty api svayam aparokṣatvāt tatrāvedyatvaṃ sūryādy-abhāsyatvenātroktaṃ, sarva-bhāsakatvena tu svayam aparokṣatvaṃ yad āditya-gataṃ teja ity atra vakṣyati | evam ubhābhyāṃ ślokābhyāṃ śruter dalad-vacaṃ vyākhyātam iti draṣṭavyam

Viśvanātha

tat padam eva kīdṛśam ity apekṣāyām āha na tad iti | auṣṇya-śaityādi-duḥkha-rahitaṃ tat sva-prakāśam iti bhāvaḥ | tan mama paramaṃ dhāma sarvotkṛṣṭam ajaḍam atīndriyaṃ tejaḥ sarva-prakāśakam | yad uktaṃ hari-vaṃśe —
tat paraṃ paramaṃ brahma sarvaṃ vibhajate jagat |
mamaiva tad ghanaṃ tejo jñātum arhasi bhārata || [HV 2.114.12] iti |
na tatra sūryo bhāti na candra-tārakaṃ
nemā vidyuto bhānti kuto ‚yam agniḥ |
tam eva bhāntam anubhāti sarvaṃ
tasya bhāsā sarvam idaṃ vibhāti || iti [KaṭhU 2.2.15] śrutibhyaś ca

Baladeva

gantavyaṃ padaṃ viśiṣyan paricāyayati na tad iti | prapannā yad gatvā yato na nivartante | tan mamaiva dhāma svarūpaṃ paramaṃ śrīmat | sarvāvabhāsakā api sūryādayas tan na bhāsayanti prakāśayanti | na tatra sūryo bhāti ity ādi-śruteś ca | sūryādibhir aprakāśyas teṣāṃ prakāśakaḥ sva-prakāśaka-cid-vigraho lakṣmīpatir aham eva pada-śabda-bodhyaḥ prapannair labhya ity arthaḥ