BhG 2.69

syntax

yā (that which) sarva-bhūtānām (of all the creatures) niśā (night) [asti] (it is),
tasyām (in that) saṁyamī (one who is restrained) jāgarti (he is awake).
yasyām (that in which) bhūtāni (creatures) jāgrati (they are awake),
sā (that) paśyataḥ (of one who is seeing) muneḥ (of a sage) niśā (night) [asti] (it is).

grammar

yā	–	yat sn. 1n.1 f. – that which;
niśā	–	niśā 1n.1 f. – night, dream;
sarva-bhūtānām	–	sarva-bhūta 6n.3 m.; sarvāṇāṁ bhūtānām iti – of all the creatures (from: sarva – all, whole; √bhū – to be, PP bhūta – been, real, world);
tasyām	–	tat sn. 7n.1 f. – in that;
jāgarti	–	√jāgṛ (to be awake, be aware) Praes. P 1v.1 – he is awake;
saṁyamī	–	saṁyamin 1n.1 m. – one who is restrained (from: sam-√yam – to hold together, to restrain, saṁyama – restraint, control);
yasyām	–	yat sn. 7n.1 f. – that in which;
jāgrati	–	√jāgṛ (to be awake, be aware) Praes. P 1v.3 – they are awake;
bhūtāni	–	bhūta (√bhū – to be) PP 1n.3 n. – beings, creatures;
sā	–	tat sn. 1n.1 f. – that;
niśā	–	niśā 1n.1 f. – night, dream;
paśyataḥ	–	paśyant (√dṛś – to see) PPr 6n.1 – of one who is seeing;
muneḥ	–	muni 6n.1 m. – of a sage, of a saint, of a seer (from: √man – to think, to imagine);

textual variants

jāgarti → jāgrati (they are awake);
yasyāṁ → tasyāṁ (in that);
jāgrati → jāgarti / jāgraṁti (is awake / are awake);
niśā → rātriḥ (night);

Śāṃkara

The key:
an excerpt from the commented verse
quotes from the scriptures
starting polemic

(6) The Universe, a mere dream to the Sajfe. In the case of the man who possesses discriminative knowledge and whose knowledge has become steady, his experience of all matters, temporal and spiritual (laukika and vaidika, sensuous and supersensuous), ceases on the cessation of nescience (avidya); for, it is the effect of nescience; and nescience ceases because it is opposed to knowledge. To make this clear, the Lord proceeds:		yo ’yaṃ laukiko vaidika ca vyavahāraḥ sa utpanna-viveka-jñānasya sthita-prajñasya avidyā-kāryatvāt avidyā-nivṛttau nivartate, avidyāyā ca vidyā-virodhāt nivṛttiḥ, ity etam arthaṃ sphuṭī-kurvann āha –
What is night to all beings, therein the self-controlled one is awake. Where all beings are awake, that is the night of the sage who sees.		yā niśā sarva-bhūtānāṃ tasyāṃ jāgarti saṃyamī | yasyāṃ jāgrati bhūtāni sā niśā paśyato muneḥ ||69||
To all beings the Supreme Reality is night. Night is by nature tamasic, and, as such, causes confusion of things. The Reality is accessible only to a man of steady knowledge.		yā niśā rātriḥ sarva-padārthānām aviveka-karī tamaḥ-svabhāvatvāt sarva-bhūtānāṃ sarveṣāṃ bhūtānām | kiṃ tat paramārtha-tattvaṃ sthita-prajñasya viṣayaḥ |
Just as what is day to others becomes night to night-wanderers, so, to all beings who are ignorant and who correspond to the night-wanderers, the Supreme Reality is dark, is like night; for it is not accessible to those whose minds are not in It.		yathā naktaṃ-carāṇām ahar eva sad anyeṣāṃ niśā bhavati, tadvat naktaṃ-cara-sthānīyānām ajñānāṃ sarva-bhūtānāṃ niśeva niśā paramārtha-tattvam, agocaratvād atad-buddhīnām |
With reference to that Supreme Reality, the self-restrained Yogin who has subdued the senses, and who has shaken off the sleep of Avidya (nescience), is fully awake.		tasyāṃ paramārtha-tattva-lakṣaṇāyām ajñāna-nidrāyāḥ prabuddho jāgarti saṃyamī saṃyamavān, jitendriyo yogīty arthaḥ |
When all beings are said to be awake, i.e., when all beings, who in reality sleep in the night of ignorance, imbued with the distinct notions of perceiver and things perceived, are as it were mere dreamers in sleep at night, – that state is night in the eye of the sage who knows the Supreme Reality; for, it is nescience itself.		yasyāṃ grāhya-grāhaka-bheda-lakṣaṇāyām avidyā-niśāyāṃ prasuptāny eva bhūtāni jāgrati iti ucyante, yasyāṃ niśāyāṃ prasuptā iva svapna-dṛśaḥ, sā niśā avidyā-rūpatvāt paramārtha-tattvaṃ paśyato muneḥ |
Works are not meant of the sage. Wherefore works are enjoined on the ignorant, not on the wise. Wisdom (Vidya) arising, nescience (Avidya) disappears as does the darkness of the night at sunrise.		ataḥ karmāṇi avidyāvasthāyām eva codyante, na vidyāvasthāyām | vidyāyāṃ hi satyām udite savitari śārvaram iva tamaḥ praṇāśam upagacchati avidyā |
Before the dawn of wisdom, nescience presents itself in various forms – as actions, means and results, – is regarded as authoritative, and becomes the source of all action. When it is regarded as of no authority, it cannot induce action.		prāk vidyotpatteḥ avidyā pramāṇa-buddhyā gṛhyamāṇā kriyā-kāraka-phala-bheda-rūpā satī sarva-karma-hetutvaṃ pratipadyate | na apramāṇa-buddhyā gṛhyamāṇāyāḥ karma-hetutvopapattiḥ |
A man engages in action regarding it as his duty – regarding that action is enjoined by such an authority as the Veda, – but not looking upon all this duality as mere illusion, as though it were night. When he has learnt to look upon all this dual world as a mere illusion, as though it were night, when he has realised the Self, his duty consists not in the performance of action, but in the renunciation of all action.		pramāṇa-bhūtena vedena mama coditaṃ kartavyaṃ karma iti hi karmaṇi kartā pravartate, na avidyā-mātram idaṃ sarvaṃ niśā iva iti | yasya punaḥ niśā iva avidyā-mātram idaṃ sarvaṃ bheda-jātam iti jñānaṃ tasya ātmajñasya sarva-karma-saṃnyāse eva adhikāro na pravṛttau |
Our Lord will accordingly show (5.17 et seq.) that such a man’s duty consists in devotion to wisdom, in jnāna-niṣṭhā.		tathā ca darśayiṣyati – tad-buddhayas tad-ātmānaḥ ity ādinā jñāna-niṣṭhāyām eva tasya adhikāram |
(Objection): – In the absence of an injunction (pravartaka pramāṇa = vidhi) one cannot have recourse to that course either. (Answer): – This objection does not apply; for, the knowledge of Atman means the knowledge of one’s own Self. There is indeed no need of an injunction impelling one to devote oneself to one’s Atman, for the very reason that Atman is one’s own very Self. And all organs of knowledge (pramaṇas) are so called because they ultimately lead to a knowledge of the Self. When the knowledge of the true nature of the Self has been attained, neither organs of knowledge nor objects of knowledge present themselves to consciousness any longer.		tatrāpi pravartaka-pramāṇābhāve pravṛtty-anupapattiḥ iti cet, na | svātma-viṣayatvād ātma-vijñānasya | na hy ātmanaḥ svātmani pravartaka-pramāṇāpekṣatā, ātmatvād eva | tad-antatvāc ca sarva-pramāṇānāṃ pramāṇatvasya | na hy ātma-svarūpādhigame sati punaḥ pramāṇa-prameya-vyavahāraḥ saṃbhavati |
For, the final authority, (viz., the Veda), teaches that the Self is in reality no percipient of objects, and while so denying, (i.e., as a result of that teaching), the Veda itself ceases to be an authority, just as the dream-perception (ceases to be an authority) in the waking state. In ordinary experience, too, we do not find any organ of knowledge necessitating further operation (on the part of the knower) when once the thing to be perceived- by that organ has been perceived.		pramātṛtvaṃ hy ātmanaḥ nivartayati antyaṃ pramāṇam | nivartayad eva cāpramāṇī-bhavati, svapna-kāla-pramāṇam iva prabodhe | loke ca vastv-adhigame pravṛtti-hetutvādarśanāt pramāṇasya | tasmān nātma-vidaḥ karmaṇy adhikāra iti siddham ||2.69||

Rāmānuja

evaṃ niyatendriyasya prasanna-manasaḥ siddhim āha—yā niśā iti | yā ātma-viṣayā buddhiḥ sarva-bhūtānāṃ niśā | niśevāprakāśā | tasyām ātma-viṣayāyāṃ buddhāv indriya-saṃyamī prasanna-manā jāgarti | ātmānam avalokayann āsta ity arthaḥ | yasyāṃ śabdādi-viṣayāyāṃ buddhau sarvāṇi bhūtāni jāgrati prabuddhāni bhavanti | sā śabdādi-viṣayā buddhir ātmānaṃ paśyato muner niśevāprakāśā bhavati

Śrīdhara

nanu na kaścid api prasupta iva darśanādi-vyāpāra-śūnyaḥ sarvātmanā nigṛhītendriyo loke dṛśyate | ato ‚saktāvitam idaṃ lakṣaṇam ity āśaṅkyāha yā niśeti | sarveṣāṃ bhūtānāṃ yā niśā | niśeva niśā ātma-niṣṭhā | ajñāna-dhvāntāvṛta-matīnāṃ tasyāṃ darśanādi-vyāpārābhāvāt | tasyāṃ ātma-niṣṭhāyāṃ saṃyamī nigṛhītendriyo jāgrati prabudhyante | sātma-tattvaṃ paśyato muner niśā | tasyāṃ darśanādi-vyāpāras tasya nāsti ity arthaḥ | etad uktaṃ bhavati – yathā divāndhānām ulukādīnāṃ rātrāv eva darśanaṃ na tu divase | evaṃ brahmajñasyonmīlitākṣasyāpi brahmaṇy eva dṛṣṭiḥ | na tu viṣayeṣu | ato nāsambhāvitam idaṃ lakṣaṇam iti

Madhusūdana

tad evaṃ mumukṣuṇā prajñā-sthairyāya prayatna-pūrvakam indriya-saṃyamaḥ kartavya ity uktaṃ sthita-prajñasya tu svataḥ siddha eva sarvendriya-saṃyama ity āha yā niśeti | yā vedānta-vākya-janita-sākṣātkāra-rūpāhaṃ brahmāsmīti prajñā sarva-bhūtānām ajñānāṃ niśeva niśā tān praty aprakāśa-rūpatvāt | tasyāṃ brahma-vidyā-lakṣaṇāyāṃ sarva-bhūta-niśāyāṃ jāgarti ajñāna-nidrāyāḥ prabuddhaḥ san sāvadhāno vartate saṃyamīndriya-saṃyamavān sthita-prajña ity arthaḥ | yasyāṃ tu dvaita-darśana-lakṣaṇāyām avidyā-nidrāyāṃ prasuptāny eva bhūtāni jāgrati svapnavad vyavaharanti sā niśā na prakāśata ātma-tattvaṃ paśyato ‚parokṣatayā muneḥ sthita-prajñasya | yāvad dhi na prabudhyate tāvad eva svapna-darśanaṃ bodhya-paryantatvād bhramasya tattva-jñāna-kāle tu na bhrama-nimittaḥ kaścid vyavahāraḥ | tad uktaṃ vārtika-kāraiḥ –

kāraka-vyavahāre hi śuddhaṃ vastu na vīkṣyante |
śuddhe vastuni siddhe ca kāraka-vyāpṛtis tathā ||
kākolūka-niśevāyaṃ saṃsāro ‚jñātma-vedinoḥ |
yā niśā sarva-bhūtānām ity avocat svayaṃ hariḥ || iti |

tathā ca yasya viparīta-darśanaṃ tasya na vastu-darśanaṃ viparīta-darśanasya vastv-adarśana-janyatvāt | yasya ca vastu-darśanaṃ tasya na viparīta-darśanaṃ viparīta-darśana-kāraṇasya vastv-adarśanasya vastu-darśanena bādhitatvāt | tathā ca śrutiḥ – yatra vā anyad iva syāt tatrānyo ‚nyat paśyet | yatra svasya sarvam ātmaivābhūt tat kena kaṃ paśyet || iti vidyāvidyayor vyavasthām āha | yathā kākasya rātry-andhasya dinam ulūkasya divāndhasya niśā rātrau paśyataś colūkasya yad dinaṃ rātrir eva sā kākasyeti mahad āścaryam etat | atas tattva-darśibhiḥ katham āvidyaka-kriyā-kārakādi-vyavahāraḥ syād iti svataḥ siddha eva tasyendriya-saṃyama ity arthaḥ

Viśvanātha

sthita-prajñasya tu svataḥ-siddha eva sarvendriya-nigraha ity āha yeti | buddhir hi dvividhā bhavati ātma-pravaṇā viṣaya-pravaṇā ca | tatra yā ātma-pravaṇā buddhiḥ sā sarva-bhūtānāṃ niśā | niśāyāṃ kiṃ kiṃ syād iti tasyāṃ svapanto janā yathā na jānanti, tathaiva ātma-pravaṇa-buddhau prāpyamāṇaṃ vastu sarva-bhūtāni na jānanti | kintu tasyāṃ saṃyamī sthita-prajño jāgarti | na tu svapiti | ata ātma-buddhi-niṣṭham ānandaṃ sākṣād anubhavati | yasyāṃ viṣaya-pravaṇāyāṃ buddhau bhūtāni jāgrati, tan-niṣṭhaṃ viṣaya-sukha-śoka-mohādikaṃ sākṣād anubhavanti na tu tatra svapanti | sā muneḥ sthita-prajñasya niśā tan-niṣṭhaṃ kim api nānubhavati ity arthaḥ | kintu paśyataḥ sāṃsārikānāṃ sukha-duḥkha-pradān viṣayān tatraudāsīnyenāvalokayataḥ svabhogyān viṣayān api yathocitaṃ nirlepam ādadānasyety arthaḥ

Baladeva

sādhakāvasthasya sthita-prajñasyendriya-saṃyamaḥ prayatna-sādhya ity uktam | siddhāvasthasya tu tasya tan-niyamaḥ svābhāvika ity āha yā niśeti | viviktātma-niṣṭhā viṣaya-niṣṭhā ceti buddhir dvividhā | yātma-niṣṭhā buddhiḥ sarva-bhūtānāṃ niśā-rūpakeṇopamātra vyajyate rātri-tulyā tadvad aprakāśikā | rātrāv ivātma-niṣṭhāyāṃ buddhau svapanto janās tal-labhyam ātmānaṃ sarve nānubhavantīty arthaḥ | saṃyamī jitendriyas tu tasyāṃ jāgarti na tu svapiti | tayā labhyam ātmānam anubhavatīty arthaḥ | yasyāṃ viṣya-niṣṭhāyāṃ buddhau bhūtānio jāgrati viṣaya-bhogān anubhavanti na tu tatra svapanti sā muneḥ sthita-prajñasya niśā | tasya viṣaya-bhogāprakāśikety arthaḥ | kīdṛśasyety āha paśyata iti | ātmānaṃ sākṣād anubhavataḥ prārabdhaākṛṣṭān viṣayān apy audāsīnyena bhuñjānasya cety arthaḥ | nartakī-mūrdha-ghaṭāvadhāna-nyāyenātma-dṛṣṭer na tad-anya-rasa-graha iti bhāvaḥ |