Numbers 1:45-54

45 So were all those who were numbered of the children of Israel, by the house of their fathers, from twenty years old and upward, all who were able to go forth to war in Israel,
46 even all those who were numbered were six hundred and three thousand and five hundred and fifty.
47 But the Levites, according to the tribe of their fathers were not numbered among them.
48 For the LORD had spoken unto Moses, saying,
49 "Only the tribe of Levi shalt thou not number, neither take the count of them among the children of Israel;
50 but thou shalt appoint the Levites over the tabernacle of testimony, and over all the vessels thereof and over all things that belong to it. They shall bear the tabernacle and all the vessels thereof, and they shall minister unto it and shall encamp round about the tabernacle.
51 And when the tabernacle setteth forward, the Levites shall take it down; and when the tabernacle is to be pitched, the Levites shall set it up; and the stranger who cometh nigh shall be put to death.
52 And the children of Israel shall pitch their tents, every man by his own camp and every man by his own standard, throughout their hosts.
53 But the Levites shall pitch round about the tabernacle of testimony, that there be no wrath upon the congregation of the children of Israel; and the Levites shall keep the charge of the tabernacle of testimony."
54 And the children of Israel did according to all that the LORD commanded Moses; so did they.