Charles Ellicott Commentary Numbers 26:7

"These are the families of the Reubenites; and they that were numbered of them were forty and three thousand and seven hundred and thirty." — Numbers 26:7 (ASV)

Forty and three thousand and seven hundred and thirty. —As compared with the former census, the tribe of Reuben had decreased by 2,770. (See Numbers 1:21.) Dathan and Abiram had probably enlisted many of the tribe to which they belonged in their rebellion against Moses and Aaron. (See Numbers 26:9-10 and Numbers 16:1.)