B.G 2.69

या निशा सर्वभूतानां तस्यां जागर्ति संयमी। यस्यां जाग्रति भूतानि सा निशा पश्यतो मुनेः ॥६९॥

yā niśā sarvabhūtānāṁ tasyāṁ jāgarti saṁyamī। yasyāṁ jāgrati bhūtāni sā niśā paśyatō munēḥ ॥69॥

Where it is night for all beings, there the self controlled is wide awake. Where the beings are awake, that is observed as night by the meditating monk.

Gīta Bhāshya 2.69

Sleeping are those who are unaware of the lord's form and characteristics. When normal beings interested in material topics are awake, it is like a night for a Jnāni. 'muni' - one who is engaged in meditation, i.e. remembering the lord. Muni observing the day as night is his accomplishment.

'yā nishā' verse describes the characteristics of a Sthitaprajna in a summarized form.

'yā niśā sarvabhūtānāṁ' i.e. that which is night for all beings, means, sleeping are those who are unaware of the lord's form and characteristics even to a limited extent. The wise Jnāni, at the same time is awake with well established transcendental knowledge and sees the supreme lord. When normal beings interested in material topics are awake, it is like a night for a Jnāni; he being asleep and not being aware.

Though such a person is purposeless like a drunk person, he exhibits conscious tendencies. Therefore, it is said:

"But this physical body in not him", "the body is under the control of the lord"

-states Bhagavata verses (Bhagavata 3.28.37-38).

'muni' is the one who is engaged in meditation, i.e. remembering the lord. By stating 'paśyataḥ', i.e. he observes as night, his accomplishment is highlighted.