Musar su Numeri 18:4

Commandment 388 imposes the duty on the Priests and Levites to guard the Tabernacle and its courtyards, etc., by day and night. This is due to considerations of respect and reverence for its sacred nature, not because of fear of intruders. The Torah writes: "They shall discharge their duties towards the Tent of Appointment" (Numbers 18,4). The Sifri interprets the words "you and your sons with you in front of the Tent of Meeting," as instructing the Priests to perform this guard duty inside the structure, whereas the Levites were to mount guard outside of it and to walk around it (18,2).

I already mentioned that a man is unable to do this on his own. He can only rouse himself in the matter and strive towards it. And this is after he has already acquired all of the previous virtuous traits we mentioned, from the beginning of Watchfulness until the Fear of Sin. Only with this will he approach the Holy and succeed. For if he lacks the previous traits, he will be like an outsider or a blemished [Kohen] of which it is stated: "an outsider (non-Kohen) shall not come near" (Bamidbar 18:4).