2.69

या निशा सर्वभूतानां तस्यां जागर्ति संयमी ।
यस्यां जाग्रति भूतानि सा निशा पश्यतो मुनेः ॥

yā niśā sarvabhūtānāṃ tasyāṃ jāgarti saṃyamī
yasyāṃ jāgrati bhūtāni sā niśā paśyato muneḥ

Kṛṣṇa (कृष्ण) is speaking.

The verse

What is night for all beings, in that the man of restraint is awake; that in which beings are awake is night for the sage who sees.

नेपालीमा

सबै प्राणीका लागि रात जे हो, त्यसमा संयमी मानिस जागा हुन्छ। प्राणीहरू जागा हुने त्यो कुरा देख्ने मुनिका लागि रात हो।

Where it sits

Their night is his waking, and their waking is his night, so the steady man is not a brighter copy of everyone else's day. 2.70 will give the ocean, and then the walk Arjuna (अर्जुन) asked for.

Split: या + निशा + सर्व-भूतानाम् + तस्याम् + जागर्ति + संयमी + यस्याम् + जाग्रति + भूतानि + सा + निशा + पश्यतः + मुनेः

yā + niśā + sarva-bhūtānām + tasyām + jāgarti + saṃyamī + yasyām + jāgrati + bhūtāni + sā + niśā + paśyataḥ + muneḥ

Sanskrit, in depth

The words

देवनागरीWordGrammarSense
याyānominative femininewhat, which. Agrees with niśā (निशा).
निशाniśānominativenight.
सर्व-भूतानाम्sarva-bhūtānāmgenitive pluralof all beings.
तस्याम्tasyāmlocative femininein that.
जागर्तिjāgartipresent, 3rd singularhe is awake.
संयमीsaṃyamīnominativethe man of restraint.
यस्याम्yasyāmlocative femininein which.
जाग्रतिjāgratipresent, 3rd pluralthey are awake.
भूतानिbhūtāninominative pluralbeings.
साsānominative femininethat.
निशाniśānominativenight.
पश्यतःpaśyataḥgenitive of the participle paśyat (पश्यत्)of the one who sees.
मुनेःmuneḥgenitiveof the sage.

The phrases

yā niśā sarvabhūtānām (या निशा सर्वभूतानाम्) is "what is night for all beings." yā (या) and niśā (निशा) are nominative. The genitive is the beings for whom it is night.

tasyāṃ jāgarti saṃyamī (तस्यां जागर्ति संयमी) is the answer. In that, the man of restraint is awake. tasyām (तस्याम्) picks up the night. The verb is singular because saṃyamī (संयमी) is one man.

yasyāṃ jāgrati bhūtāni (यस्यां जाग्रति भूतानि) reverses it. That in which beings are awake. The verb is plural because bhūtāni (भूतानि) is plural. yasyām (यस्याम्) is "in which," locative like tasyām (तस्याम्).

सा निशा पश्यतः मुनेः sā niśā paśyato muneḥ closes the reversal. That is night for the seeing sage. sā (सा) answers yā (या). paśyataḥ (पश्यतः) and muneḥ (मुनेः) are one man in the genitive, the sage who sees.

Sanskrit in this line

jāgarti (जागर्ति) is singular, jāgrati (जाग्रति) is plural, and the verses are two sentences so you can hear it. The man of restraint is one, so the verb is jāgarti (जागर्ति). The beings are many, so the verb is jāgrati (जाग्रति). Same root, jāgṛ (जागृ). The ending tells you who is awake before you finish the noun. yā (या) ... tasyām (तस्याम्), and yasyām (यस्याम्) ... sā (सा), are two correlative frames, not one tangled sentence.

Say it back

Whose night he wakes in, and whose waking is night for him. If both verbs come out singular, the beings have disappeared.