BhG 13.17

syntax

tad [jñeyam] (that to be known) jyotiṣām api (even among lights) jyotiḥ [asti] (it is light),
tamasaḥ (than darkness) param (higher) ucyate (it is said),
jñānam (knowledge) jñeyam (to be known) jñāna-gamyam (accessible by knowledge) sarvasya (of all) hṛdi (in the heart) viṣṭhitam (situated).

grammar

jyotiṣām	–	jyotiḥ 6n.3 n. – among lights, brightness, among stars;
api	–	av. – although, moreover, besides, even;
tat	–	tat sn. 1n.1 n. – that;
jyotiḥ	–	jyotiḥ 1n.1 n. – light, brightness, fire, eye;
tamasaḥ	–	tamas 5n.1 n. – than darkness, gloom, dullness, passivity, one of the three guṇas (from: √tam – to choke, to faint, to perish, to stop);
param	–	para 1n.1 n. – beyond, ancient, final, the best, the supreme; av. – later, next, future (from: para – beyond, ancient, final, the best, the supreme);
ucyate	–	√vac (to speak) Praes. pass. 1v.1 – it is said;
jñānam	–	jñāna 1n.1 n. – knowledge, wisdom, intelligence (from: √jñā – to know, to understand);
jñeyam	–	jñeya (√jñā – to know, to understand) PF 1n.1 n. – to be known, to be learnt;
jñāna-gamyam	–	jñāna-gamya 1n.1 n.; TP: jñānena gamyam iti – to be reached by knowledge (from: √jñā – to know, to understand, jñāna – knowledge, wisdom, intelligence; √gam – to go, PF gamya – to be gone to, to be reached, attainable);
hṛdi	–	hṛt 7n.1 n. – in the heart, in the self;
sarvasya	–	sarva sn. 6n.1 n. – of all;
viṣṭhitam	–	vi-ṣṭhita (vi-√sthā – to be present) PP 1n.1 n. – situated;

textual variants

taj jyotis → taj yonis (that source);
tamasaḥ → tamasā (by the darkness);
jñānaṁ jñeyaṁ → jñāna-jñeyaṁ (knowledge to be known);
hṛdi sarvasya → sarvasya hṛdi / hṛdi sarvatra (in the heart of all / in the heart everywhere);
viṣṭhitam → madhya-gam / veṣṭitaṁ / dhiṣṭhitaṁ (which has gone inside / gone / situated);

Śāṃkara

kiṃ ca, sarvatra vidyamānam api san nopalabhyate cet, jñeyaṃ tamas tarhi ? na | kiṃ tarhi ?—
jyotiṣām ādity-ādīnām api taj jñeyaṃ jyotiḥ | ātma-caitanya-jyotiṣeddhāni hy ādity-ādīni jyotīṃṣi dīpyante, yena sūryas tapati tejaseddhaḥ [sthitaittbhāvr 3.12.9], tasya bhāsā sarvam idaṃ vibhāti [śāstrvetuttaṃ 6.14] īty ādi-śrutibhyaḥ | smṛte ca ihaiva—yad āditya-gataṃ tejaḥ [gītā 15.12] ity ādeḥ | tamaso’jñānāt param aspṛṣṭam ucyate | jñānāder duḥsaṃpādana-buddhyā prāptāvasādasyottambhanārtham āha—jñānam amānitvādi | jñeyaṃ jñeyaṃ yat tat pravakṣyāmīty [gītā 13.13] ādinoktam | jñāna-gamyaṃ jñeyam eva jñātaṃ saj jñāna-phalam iti jñāna-gamyam ucyate | jñāyamānaṃ tu jñeyam | tad etat trayam api hṛdi buddhau sarvasya prāṇi-jātasya viṣṭhitaṃ viśeṣeṇa sthitam | tatraiva hi trayaṃ vibhāvyate

Rāmānuja

jyotiśām dīpādityamaṇiprabhṛtīnām api tad eva jyotiḥ prakāśakam, dīpādityādīnām apy ātmaprabhārūpaṃ / jñānam eva prakāśakam / dīpādayas tu viṣayendriyasannikarṣavirodhisaṃtamasanirasanamātraṃ kurvate / tāvan mātreṇa teṣāṃ prakāśakatvam / tamasaḥ param ucyate / tamaśśabdaḥ sūkṣmāvasthaprakṛtivacanaḥ / prakṛteḥ param ucyata ityarthaḥ / ato jñānaṃ jñeyaṃ jñānaikākāram iti jñeyam / tac ca jñānagamyam amānitvādibhir jñānasādhanair uktaiḥ prāpyam ityarthaḥ / hṛdi sarvasya viṣṭhitam sarvasya manuṣyādeḥ hṛdi viśeṣaṇāvasthitam sannihitam

Śrīdhara

kiṃ ca jyotiṣām apīti | jyotiṣāṃ sūryādīnām api jyotiḥ prakāśakaṃ tat | yena sūryas tapati tejasendhaḥ |
na tatra sūryo bhāti na candra-tārakaṃ
nemā vidyuto bhānti kuto ‚yam agniḥ |
tad eva bhāntam anubhāti sarvaṃ
tasya bhāsā sarvam idaṃ vibhāti || [KaṭhU 2.5.15] ity ādi-śruteḥ |
ataeva tamaso ‚jñānāt paraṃ tenāsaṃsṛṣṭam ucyate | āditya-varṇaṃ tamsasaḥ parastāt ity ādi-śruteḥ | jñānaṃ ca tad eva buddhi-vṛttau abhivyaktam | tad eva rūpādy-ākāreṇa jñeyaṃ ca jñāna-gamyaṃ ca | amānitvādi-lakṣaṇena pūrvokta-jñāna-sādhanena prāpyam ity arthaḥ | jñāna-gamyaṃ viśinaṣṭi sarvasya prāṇimātrasya hṛdi viṣṭhitaṃ viśeṣeṇāpracyuta-svarūpeṇa niyantṛtayā sthitam | dhiṣṭhitam iti pāṭhe adhiṣṭāya sthitim ity arthaḥ |

Madhusūdana

nanu sarvatra vidyamānam api tan nopalabhyate cet tarhi jaḍam eva syāt, na syāt svayaṃjyotiṣo ‚pi tasya rūpādi-hīnatvenendriyādy-agrāhyatvopapatter ity āha jyotiṣām iti | taj jñeyaṃ brahma jyotiṣām avabhāsakānām ādityādīnāṃ buddhy-ādīnāṃ ca bāhyānām āntarāṇām api jyotir avabhāsakaṃ caityanya-jyotiṣo jaḍa-jyotir-avabhāsakatvopapatteḥ | yena sūryas tapati tejasendhaḥ | tasya bhāsā sarvam idaṃ vibhāti [KaṭhU 2.5.15] ity ādi-śruteś ca | vakṣyati ca yad āditya-gataṃ tejaḥ [Gītā 15.8] ity ādi |
svayaṃ jaḍatvābhāve ‚pi jaḍa-saṃsṛṣṭaṃ syād iti nety āha tamaso jaḍa-vargāt param avidyā-tat-kāryābhyām apāramārthikābhyām asaṃspṛṣṭaṃ pāramārthikaṃ tad brahma sad-asatoḥ sambandhāyogāt | ucyate akṣarāt parataḥ paraḥ ity ādi-śrutibhir brahma-vādibhiś ca | tad uktam –
niḥsaṅgasya sa-saṅgena kūṭasthasya vikāriṇā |
ātmano ‚nātmanā yogo vāstavo nopapadyate ||
āditya-varṇaṃ tamasaḥ parastāt iti śruteś ca | āditya-varṇam iti sva-bhāne prakāśāntarānapekṣaṃ sarvasya prakāśakam ity arthaḥ | yasmāt tat svayaṃ jyotir jaḍāsaṃspṛṣṭam ata eva taj jñānaṃ pramāṇa-janya-ceto-vṛtty-abhivyakta-saṃvid-rūpam | ata eva tad eva jñeyaṃ jātum arham ajñātatvāj jaḍasyājñātatvābhāvena jñātum anarhatvāt | kathaṃ tarhi sarvair na jñāyate tatrāha jñāna-gamyaṃ pūrvoktenāmānitvādinā tattva-jñānārtha-darśanāntena sādhana-kalāpena jñāna-hetutayā jñāna-śabditena gamyaṃ prāpyaṃ na tu tad vinety arthaḥ |
nanu sādhanena gamyaṃ cet tat kiṃ deśāntara-vyavahitam ? nety āha hṛdi sarvasya viṣṭhitaṃ sarvasya prāṇi-jātasya hṛdi buddhau viṣṭhitaṃ sarvatra sāmānyena sthitam api viśeṣa-rūpeṇa tatra sthitam abhivyaktaṃ jīva-rūpeṇāntaryāmi-rūpeṇa ca | sauraṃ teja ivādarśa-sūrya-kāntādau | avyavahitam eva vastuto bhrāntyā vyavahitam iva sarva-bhrama-kāraṇājñāna-nivṛttyā prāpyata ivety arthaḥ

Viśvanātha

jyotiṣāṃ candrādityānām api taj jyotiḥ prakāśakaṃ | yena sūryas tapati tejasendhaḥ |
na tatra sūryo bhāti na candra-tārakaṃ
nemā vidyuto bhānti kuto ‚yam agniḥ |
tad eva bhāntam anubhāti sarvaṃ
tasya bhāsā sarvam idaṃ vibhāti || [KaṭhU 2.5.15] ity ādi-śruteḥ |
ata eva tamaso ‚jñānāt paraṃ tenāsaṃsṛṣṭam ucyate | āditya-varṇaṃ tamsasaḥ parastāt ity ādi-śruteḥ | jñānaṃ tad eva buddhi-vṛttau abhivyaktaṃ sat jñānam ucyate | tad eva rūpādy-ākāreṇa pariṇataṃ jñeyaṃ ca | tad eva jñāna-gamyaṃ pūrvoktenāmānitvādi-jñāna-sādhanena prāpyam ity arthaḥ | tad eva paramātma-svarūpaṃ sat sarvasya prāṇimātrasya hṛdi dhiṣṭhitaṃ niyantṛtayādhbiṣṭhāya sthitam ity arthaḥ

Baladeva

jyotiṣāṃ sūrydīnām api tad brahma jyotiḥ prakāśakaṃ |
na tatra sūryo bhāti na candra-tārakaṃ
nemā vidyuto bhānti kuto ‚yam agniḥ |
tad eva bhāntam anubhāti sarvaṃ
tasya bhāsā sarvam idaṃ vibhāti || [KaṭhU 2.5.15]
ity ādi-śrutes tad brahma | tad brahma tamasaḥ prakṛteḥ paraṃ tenāspṛṣṭam ucyate āditya-varṇaṃ tamasaḥ parastāt [ŚvetU 3.8] ity śrutyā | jñānaṃ cid-eka-rasam ucyate vijñānam ānanda-ghanaṃ brahma [GTU 2.79?] iti śrutyā | jñānaṃ mumukṣoḥ śaraṇatvena jñātum arham ucyate taṃ ha devam ātma-buddhi-prakāśaṃ mumukṣur vai śaraṇam ahaṃ prapadye [GTU 1.25] iti śrutyā | jñāna-gamyam ucyate tam eva viditvātimṛtyum eti [ŚvetU 3.8] iti śrutyā | sarvasya prāṇi-mātrasya hṛdi dhiṣṭhitaṃ niyantṛtayādhiṣṭhāya sthitam ity ucyate antaḥ-praviṣṭaḥ śāstā janānām [TaittĀ 3.11.10] iti śrutyā | na ca sarvataḥ pāṇīty ādi pañcakaṃ jīva-paratayaiva neyaṃ tat-prakaraṇatvādi-vācyaṃ jīvavad īśvarasyāpi kṣetrajñatvena prakṛtatvāt | sarvataḥ pāṇīty ādi-sārdhakasya brahmaivopakramya śvetāśvataraiḥ paṭhitvāt prakaraṇa-śāvalyasyopaniṣatsu vīkṣaṇāc ca