What is night for all beings, in that the self-controlled person is awake. What is waking for all beings, that is night for the sage who sees.
Explanation
Krishna is describing the person of steady wisdom (sthitaprajña) to Arjuna. "Night" is a figure for what most people overlook: the self-controlled person (saṃyamī) is alert to the Self and to inner truth, while ordinary people are absorbed in sense pleasures and pursuits, which the sage sees through as a kind of sleep. Traditional commentators generally read the two states, night and waking, as the Self versus worldly life, though they differ in how they describe the sage's awareness.