Numbers 32:2

“The children of Gad and the children of Reuben came and spake unto Moses, etc.] The children of Gad are mentioned first, though Reuben was the firstborn, and had a standard under which Gad pitched: it may be, as Aben Ezra thinks, the Gadites were the first authors of this counsel, the contrivers of this scheme; who first moved it to the Reubenites, which they had an opportunity of doing, lying encamped by them; or however, they might be the most busy and active in this affair, or the best spokesmen; for it could be only some, in the name of the whole, that addressed Moses on this account, and spoke to him about it: and to Eleazar the priest, and unto the princes of the congregation; who…”