Numbers 10:14-17

Judah was set out first, not Reuben. Right behind Judah was Issachar, and right behind those two was Zebulun. Very interestingly, the next tribe in line was two-thirds of the tribe of Levi. Levi is not named, but two of his sons are named in verse 17: Gershon and Merari. It also stipulates what they are doing in the marching order. They are carrying the tabernacle. It had to be broken down into all of its pieces, and distributed among those two tribes. They had to hoist them onto their shoulders, and when they were marching, those two tribes (both sons of Levi) were carrying the entire tabernacle in all its various pieces on their shoulders.