Altar of Witness
"So the Reubenites and the Gadites and the half-tribe of Manasseh [see Children of Jacob] returned home, parting from the people of Israel at Shiloh, which is in the land of Canaan, to go to the land of Gilead, their own land of which they had possessed themselves by command of The Lord [see Rock Of Ages] through Moses. And when they came to the region about the Jordan, that lies in the land of Canaan, the Reubenites and the Gadites and the half-tribe of Manasseh built there an altar by the Jordan, an altar of great size. And the people of Israel heard say, "Behold, the Reubenites and the Gadites and the half-tribe of Manasseh have built an altar at the frontier of the land of Canaan, in the region about the Jordan, on the side that belongs to the people of Israel." And when the people of Israel heard of it, the whole assembly of the people of Israel gathered at Shiloh, to make war against them." (Joshua 22:9-12 RSV)
Don't Forget, Our Land Is Israel Too
The first part of the God-Commanded Promised Land was actually taken east of The Jordan River, in the land of Gilead. It was given to the tribes of Reuben, Gad and part of Manasseh - who then continued on with the other tribes to assist them in the taking of their territory, in Canaan, west of the Jordan, just as the other tribes had assisted the taking of the land east of the Jordan. When all was done, the two and a half tribes returned back across the Jordan to their part of the Promised Land, but concerned that it would be forgotten that their territory was as much Israel as that on the other side of the river (which has happened), they built an altar to serve as a reminder of their unity - but which was at first misunderstood by the others.
"Then the Reubenites, the Gadites, and the half-tribe of Manasseh said in answer to the heads of the families of Israel, "The Mighty One, God, The Lord! The Mighty One, God, The Lord! He knows; and let Israel itself know! If it was in rebellion or in breach of faith toward The Lord, spare us not today for building an altar to turn away from following The Lord; or if we did so to offer burnt offerings or cereal offerings or peace offerings on it, may The Lord Himself take vengeance."
"Nay, but we did it from fear that in time to come your children might say to our children, 'What have you to do with The Lord, the God of Israel? For The Lord has made the Jordan a boundary between us and you, you Reubenites and Gadites; you have no portion in The Lord.' So your children might make our children cease to worship The Lord."
"Therefore we said, 'Let us now build an altar, not for burnt offering, nor for sacrifice, but to be a witness between us and you, and between the generations after us, that we do perform the service of The Lord in his presence with our burnt offerings and sacrifices and peace offerings; lest your children say to our children in time to come, "You have no portion in The Lord."'
"And we thought, If this should be said to us or to our descendants in time to come, we should say, 'Behold the copy of the altar of The Lord, which our fathers made, not for burnt offerings, nor for sacrifice, but to be a witness between us and you.'"
"Far be it from us that we should rebel against The Lord, and turn away this day from following The Lord by building an altar for burnt offering, cereal offering, or sacrifice, other than the altar of The Lord our God that stands before his tabernacle!"
"When Phinehas the priest and the chiefs of the congregation, the heads of the families of Israel who were with him, heard the words that the Reubenites and the Gadites and the Manassites spoke, it pleased them well. And Phinehas the son of Eleazar the priest said to the Reubenites and the Gadites and the Manassites, "Today we know that The Lord is in the midst of us, because you have not committed this treachery against The Lord; now you have saved the people of Israel from the hand of The Lord."
"Then Phinehas the son of Eleazar the priest, and the chiefs, returned from the Reubenites and the Gadites in the land of Gilead to the land of Canaan, to the people of Israel, and brought back word to them. And the report pleased the people of Israel; and the people of Israel blessed God and spoke no more of making war against them, to destroy the land where the Reubenites and the Gadites were settled."
"The Reubenites and the Gadites called the altar Witness; "For," said they, "it is a witness between us that The Lord is God." (Joshua 22:21-34 RSV)
Fact Finder: How does the national territory of Israel today compare to that in the time of King David and King Solomon?
See Solomon's Kingdom