Adam Clarke on Exodus 18:23

If thou shalt do this thing, and God command thee - Though the measure was obviously of the utmost importance, and plainly recommended itself by its expediency and necessity; yet Jethro very modestly leaves it to the wisdom of Moses to choose or reject it; and, knowing that in all things his relative was now acting under the immediate direction of God, intimates that no measure can be safely adopted without a positive injunction from God himself. As the counsel was doubtless inspired by the Divine Spirit, we find that it was sanctioned by the same, for Moses acted in every respect according to the advice he had received.