Joshua 4:12
And the children of Reuben, and the children of Gad, and half the tribe of Manasseh, passed over armed before the children of Israel, as Moses spake unto them: And the children of Reuben, and the children of Gad, and half the tribe of Manasseh, passed over armed before the children of Israel, as Moses spake unto them:
The descendants of Reuben and Gad, together with the half tribe of Manasseh, crossed the Jordan armed and in advance of the rest of Israel. They did so in obedience to the command given through Moses and in fulfillment of their pledge to aid their brethren in the warfare until those brethren had also received their inheritance. About forty thousand of them went over prepared for battle onto the plains of Jericho. They fought faithfully alongside the other tribes through the years of conquest, and afterward returned to their families and their own lands bearing a share of the spoils.
The passage through the river was a deliverance wrought by God. Stones lifted from the riverbed were erected as an enduring memorial of it. That witness was appointed so that succeeding generations would be told what God had done and would acknowledge His power.