12 And the children of Reuben, and the children of Gad, and the half tribe of Manasseh, went over in array before the children of Israel, as Moses had spoken to them. 13 About forty thousand armed for military service passed over before Jehovah to the war, unto the plains of Jericho.
Matthew Henry's Commentary on Joshua 4:12-13
Commentary on Joshua 4:10-19
(Read Joshua 4:10-19)
The priests with the ark did not stir till ordered to move. Let none be weary of waiting, while they have the tokens of God's presence with them, even the ark of the covenant, though it be in the depths of adversity. Notice is taken of the honour put upon Joshua. Those are feared in the best manner, and to the best purpose, who make it appear that God is with them, and that they set him before them.