This appointment of the “captains” (compare Exodus 18:21 ff) must not be confounded with that of the elders in Numbers 11:16 ff. The former would number 78,600; the latter were 70 only.
A comparison between this passage and that in Exodus makes it obvious that Moses is only touching on certain parts of the whole history, without regard to order of time, but with a special purpose. This important arrangement for the good government of the people took place before they left Horeb to march direct to the promised land. This fact sets more clearly before us the perverseness and ingratitude of the people, to which the orator next passes; and shows, what he was anxious to impress, that the fault of the 40 years‘ delay rested only with themselves!