A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
jos 22:1JOSHUA DISMISSES THE TWO TRIBES AND A HALF, WITH A BLESSING. (Jos 22:1-9)
Then Joshua called the Reubenites, and the Gadites, and the half tribe of Manasseh--The general war of invasion being ended and the enemy being in so dispirited and isolated a condition that each tribe, by its own resources or with the aid of its neighboring tribe, was able to repress any renewed hostilities, the auxiliary Israelites from the eastern side of the Jordan were now discharged from service. Joshua dismissed them with high commendations for their fidelity and earnest admonitions to cultivate perpetual piety in life. The redundancy of the language is remarkable [Jos 22:2-5]. It shows how important, in the judgment of the venerable leader, a steadfast observance of the divine law was to personal happiness, as well as national prosperity.
jos 22:3Ye have not left your brethren these many days unto this day--for the space of seven years.
jos 22:4get you unto your tents--that is, home; for their families had been left in fortified towns (Num 32:17).
jos 22:8he spake unto them, saying, Return with much riches--in cattle, clothes, and precious metals.
divide the spoil of your enemies with your brethren--(See on Num 31:25-39).
jos 22:10THEY BUILD THE ALTAR OF TESTIMONY ON THEIR JOURNEY. (Jos 22:10)
when they came unto the borders of Jordan, that are in the land of Canaan, the children of Reuben . . . built there an altar by Jordan--This altar was probably an immense pile of stones and earth. The generality of our translators supposes that it was reared on the banks of the Jordan, within the limits of Canaan proper. But a little closer examination seems to make the conclusion irresistible that its position was on the eastern side of the river, for these two reasons; first, because it is said (Jos 22:11) to have been built "over against," or in the sight of the land of Canaan--not within it; and secondly, because the declared motive of the trans-jordanic Israelites in erecting it was to prevent their brethren in Canaan ever saying, "in time to come, What have ye to do with the Lord God of Israel? For the Lord hath made Jordan a border between us and you," &c. [Jos 22:24-25]. Such a taunt would be obviously prevented or confuted by the two tribes and a half having on the eastern side of Jordan, within their own land, a facsimile of the altar at Shiloh, as a witness that they acknowledged the same God and practised the same rites of worship as the brethren in Canaan.
jos 22:11CONTENTION THEREUPON. (Jos. 22:11-29)
and the children of Israel heard say--Fame speedily spread intelligence of what the trans-jordanic tribes had done. The act being suspected of some idolatrous design, the tribes rose in a mass, and repairing to the tabernacle at Shiloh, resolved to declare war against the two tribes and a half as apostates from God. On calmer and more mature consideration, however, they determined, in the first instance, to send a deputation consisting of the son of the high priest, and ten eminent persons from each tribe, to make inquiry into this rumored rebellion against God (Deu 13:13-15). The quality of the deputies evinced the deep solicitude that was felt on the occasion to maintain the purity of the divine worship throughout Israel. In the presumptive belief that the two tribes and a half had really built an altar, the deputies expressed astonishment at their so soon falling into such a heinous crime as that of violating the unity of divine worship (Exo 20:24; Lev 17:8-9; Deu 12:5-13). They reminded their eastern brethren of the disastrous consequences that were entailed on the nation at large by the apostasy at Peor and by the sin of Achan, and finally exhorted them, if they felt the want of the tabernacle and altar and repented of their rash choice in preferring worldly advantages to religious privileges, to remove to the western side of the Jordan, where all the tribes would form a united and obedient community of worshippers.
jos 22:21Then the children of Reuben . . . answered--repudiating, in the strongest terms, the alleged crime, and deponing that so far from entertaining the intention imputed to them, their only object was to perpetuate the memory of their alliance with Israel [Jos 22:24-25], and their adherence to the worship of Israel's God [Jos 22:26-27].
jos 22:33THE DEPUTIES SATISFIED. (Jos 22:30-34)
the thing pleased the children of Israel--The explanation not only gave perfect satisfaction to the deputies, but elicited from them expressions of unbounded joy and thankfulness. "This day we perceive that the Lord is among us" [Jos 22:31], that is, by His gracious presence and preventing goodness, which has kept you from falling into the suspected sin and rescued the nation from the calamity of a fratricidal war or providential judgments. This episode reflects honor upon all parties and shows that piety and zeal for the honor and worship of God animated the people that entered Canaan to an extent far beyond what was exemplified in many other periods of the history of Israel.