Charles Ellicott Commentary Numbers 1:48

"For Jehovah spake unto Moses, saying," — Numbers 1:48 (ASV)

For the Lord had spoken ... — Better, And the Lord spoke.... (Numbers 3:1; Numbers 3:5–6; Numbers 3:14–15). It is true that the Levites were not included in the earlier numbering, and consequently that they must have been exempted by divine direction. It does not appear, however, that there is a reference to any previous command respecting the Levites, or that the specific destination of the Levites had been previously declared.