And the LORD spake unto Moses in the wilderness of Sinai, saying,
Number the children of Levi. They were numbered as well as the other tribes, but the enumeration was made on a different principle; for while in the other tribes the amount of males was calculated from twenty years and upward, in that of Levi they were counted from a month old and upwards. The reason of the distinction is obvious. In the other tribes the survey was made for purposes of war, from which the Levites were totally exempt, and were appointed to a work on which they entered as soon as they were capable of instruction (cf. 1 Samuel 1:28).
They are mentioned under the names of Gershon, Kohath, and Merari, sons of Levi, and chiefs or ancestral heads of three subdivisions into which this tribe was distributed. Their duties were to assist in the conveyance of the tabernacle when the people were removing the various encampments, and to form its guard while stationary-the Gershonites being stationed on the west, the Kohathites on the south, and the families of Merari on the north. The Kohathites had the principal place about the tabernacle, and charge of the most precious and sacred things-a distinction with which they were honoured, probably, from the Aaronic family belonging to this division of the Levitical tribe. The Gershonites being the oldest, had the next honourable post assigned them, while the burden of the drudgery was thrown on the division of Merari.
Verse 21. The Shimites. This Levitical family, descended from Shimei or Shimi (Numbers 3:18: cf. Exodus 6:17), is supposed to be the root from which sprang Shimei mentioned in 1 Chronicles 3:19 and Zechariah 12:13.