Why does the manas, which engages in continual scrutiny and deliberation, still require sleep?

Sleep is for restoring the physical body's energy and eliminating its fatigue, so that the six consciousnesses can operate normally, better, and more effectively. The manas regards the physical body as its own possession, regards the six consciousnesses as its own possessions, and regards all of the five aggregates and eighteen realms as its own possessions; it also relies on the eighth consciousness to know the condition of the physical body from moment to moment. The activity of the six consciousnesses consumes energy; in order to reduce this energy consumption, the manas decides not to let the six consciousnesses continue their activity, and proactively shuts off the six consciousnesses' discernment of the six sense objects, no longer wishing to know the six sense objects—relying only on the manas's own knowing. In this way, energy continuously accumulates, and once vitality has recovered to a certain degree, the manas will decide to wake up, make contact with sense objects, and continue the activities of the five aggregates.

If the physical body is fatigued, sleep is needed to restore energy, and the manas will decide to sleep and not let the six consciousnesses continue their activity; the manas itself wishes to shut off the six sense objects and not discern them, and thus the five sense consciousnesses and the mind consciousness will gradually cease. Therefore, it is not that the manas needs to sleep, but that the physical body needs rest, to replenish energy and restore vitality. This is precisely the result of the manas's continual scrutiny and deliberation. Yet sleep does not affect the manas's continual scrutiny and deliberation; the manas can continue deliberating during sleep, and can also manifest dream states, deliberating within them.