Tamāla Kṛṣṇa: 69: "What is night for all beings is the time of awakening for the self-controlled, and the time of awakening for all beings is the night for the introspective sage." Purport: "There are two classes of intelligent men. The one is intelligent in material activities for sense gratification, and the other is introspective and awake to the cultivation of self-realization. Activities of the introspective sage or thoughtful man are night for persons materially absorbed. Materialistic persons remain asleep during such a night due to their ignorance of self-realization. The introspective sage, however, remains alert in that night of the materialistic man."
Prabhupāda: Night means when people sleep, and day means when they are awake. This is the understanding of day and night. So one, the materialistic persons, they are sleeping in the matter of spiritual understanding. So therefore the activities which we find in daytime of the materialistic person, actually that is night. For the spiritualistic person, they see that these people they got the facility of self-realization, this human form of life. How they are wasting by sleeping. And the materialistic persons, they are seeing, "Oh, these Kṛṣṇa conscious young boys, they have given up everything and they are chanting Hare Kṛṣṇa. How nonsense. They are sleeping." So you see? So in the vision of the materialistic person, these activities are night, sleeping. And for the self-realized person, these activities are sleeping. You see? Just the opposite. They are seeing the Kṛṣṇa conscious person as wasting time and the Kṛṣṇa conscious person is seeing them as wasting time. This is the position.