Numbers 10:31

Or, this is to be understood of his directing them not so much in their way. as about great and difficult matters, wherein the counsel he had from God did not exclude the advice of men, as we see in Hobab's father Jethro, Exod. xviii, 19-27. And it is probable, this was the wise son of a wise father.

And he said,....

Even those that were led by miracle must not slight the ordinary means of direction. Some think that Moses suggests this to Hobab, not because he expected much benefit from his information, but to please him with the thought of being some way useful to so great a body, and so to draw him on with them, by inspiring him with an ambition to obtain that honour.

Besides, several detachments were sent off from the main body; the services of Hobab, not as a single Arab, but as a prince of a powerful clan, would have been exceedingly useful.

Thou mayest be to us instead of eyes - But what need had they of Hobab, when they had the pillar and fire continually to point out their way? Answer: The cloud directed their general journeys, but not their particular excursions. Parties took several journeys while the grand army lay still. (See Numbers 13, 20, 31, 32, etc). They therefore needed such a person as Hobab, who was well acquainted with the desert, to direct these particular excursions; to point them out watering places, and places where they might meet with fuel, etc., etc. What man cannot, under the direction of God’s providence, do for himself, God will do in the way of especial mercy. He could have directed them to the fountains and to the places of fuel, but Hobab can do this, therefore let Hobab be employed; and let Hobab know for his encouragement that, while he is serving others in the way of God’s providence, he is securing his own best interests. On these grounds Hobab should be invited, and for this reason Hobab should go. Man cannot do God’s work; and God will not do the work which he has qualified and commanded man to perform. Thus then the Lord is ever seen, even while he is helping man by man. See some valuable observations on this subject in Harmer, vol. ii., 286. Instead of, And thou mayest be to us instead of eyes, the Septuagint translate the passage thus: Και εσῃ εν ἡμιν πρεσβυτης, And thou shalt be an elder among us. But Moses probably refers to Hobab’s accurate knowledge of the wilderness, and to the assistance he could give them as a guide.