Numbers 1:47 - Coke's Commentary on the Holy Bible

But the Levites—were not numbered— We find in chap. Numbers 3:16, &c. that the Levites were to keep a distinct register of their own; though, as being separated from the rest of their brethren for the service of the tabernacle, and therefore excused from war, they are not numbered here with those who were to go to war, Numbers 1:3. In all nations, the ministers of religion have been exempted from war, as incongruous to their profession. Strabo notes this custom to have been as old as Homer's time; and Caesar observes of the ancient Druids in Britain, that they were freed not only from the wars, but from tribute also: Druides a bello abesse consueverunt; neque tributa una cum reliquis pendunt, militiae vacationem omniumque rerum habent immunitatem. "The Druids were never engaged in military affairs, neither did they bear any part of the public taxes, but were allowed a perfect immunity and leisure, both from war, and from all civil employments." Caes. de Bell. Gall. lib. vi. c. 13.