Able men. Literally, "men of might"—i.e; of capacity or ability—men competent for the office of judge; who are further defined to be, such as possess the three qualities of piety, veracity, and strict honesty, or incorruptness.
Jethro's conception of the true judicial character leaves little to be desired. If among every ten Israelites there was one such person, the moral condition of the nation cannot have been so much depressed by the Egyptian servitude as is sometimes represented.
Place such over them to be rulers of thousands, etc. A decimal organisation naturally presents itself to men's minds as the simplest in a simple state of society, and was probably already in use among the Arab tribes with whom Jethro was familiar.
The graduated series—rulers of tens, of fifties, of hundreds, and of thousands, implies a power of three-fold appeal, from the "ruler of ten" to the "ruler of fifty"—from him to the "ruler of a hundred"—and from him to the "ruler of a thousand."
Whether there was an appeal from the last-named to Moses, is doubtful. Probably there was not; Moses deciding those cases only which the "rulers of thousands" reserved for him as being specially difficult or important.