Moses at the census did not take into consideration the tribe of Levi, because God had not commanded him to select a prince for this tribe as for all others, hence he drew the conclusion that they were not to be counted. Naturally he was not sure of his decision in this matter, and wavered whether or not to include the Levites in the number, when God said to him: "Do not muster the tribe of Levi, nor number them among the children of Israel."
At these words Moses was frightened, for he feared that his tribe was considered unworthy of being counted with the rest, and was therefore excluded by God. But God quieted him, saying: "Do not number the Levites among the children of Israel, number them separately." There was several reasons for numbering the Levites separately. God foresaw that, owing to the sin of the spies who were sent to search the land, all men who were able to go to war would perish in the wilderness, "all that were numbered of them, according to their whole number, from twenty years old and upward."
Now had the Levites been included in the sum total of Israel, the Angel of Death would have held sway over them also, wherefore God excluded them from the census of all the tribes, that they might in the future be exempt from the punishment visited upon the others, and might enter the promised land. The Levites were, furthermore, the body-guard of God, to whose care the sanctuary was entrusted-another reason for counting them separately.
God in this instance conducted Himself like the king who ordered one of his officers to number his legions, but added: "Number all the legions excepting only the legion that is about me."