“Every night of Yom Kippur the High Priest would sit and expound if he was a Torah scholar, and if he was a Torah student, they would expound to him . . . so that he would not sleep.”

Besides physical sleep, there is also spiritual sleep. Spiritual sleep is the attempt to rise above worldy matters and withdraw from them, just as during sleep the soul withdraws from the body and ascends on high.

Guarding the High Priest from sleep means that if they see an ascetic impulse in him they remind him that asceticism is not the way, for the Creator demands involvement in wordly matters to purify them and elevate them, not withdrawal.

(Likkutei Sichot, vol. 2, p. 650)