Numbers 31:6 - Clarke's commentary and critical notes on the Bible

And Moses sent them to the war, a thousand of every tribe, them and Phinehas the son of Eleazar the priest, to the war, with the holy instruments, and the trumpets to blow in his hand. A thousand of every tribe - Twelve thousand men in the whole. And Phinehas, the son of Eleazar; some think he was made general in this expedition, but this is not likely. The ark and its contents must proceed to this battle, because the battle was the Lord's, and he dwelt between the cherubim over the ark; and Phinehas, who had before got a grant in the eternal priesthood, was chosen to accompany the ark in place of his father Eleazar, who was probably now too far advanced in years to undergo the fatigue. Who then was general? Joshua, without doubt, though not here mentioned, because the battle being the Lord's, he alone is to have the supreme direction, and all the glory. Besides, it was an extraordinary war, and not conducted on the common principle, for we do not find that peace was offered to the Midianites, and that they refused it; see Deuteronomy 20:10, etc. In such a case only hostilities could lawfully commence; but they were sinners against God; the cup of their iniquity was full, and God thought proper to destroy them. Though a leader there certainly was, and Joshua was probably that leader, yet because God, for the above reason, was considered as commander-in-chief, therefore no one else is mentioned; for it is evident that the sole business of Phinehas was to take care of the holy instruments and to blow with the trumpet.