To go up to war against them - Supposing that they had built this altar in opposition to that which Moses, by the command of God, had erected, and were consequently become rebels against God and the Israelitish constitution, and should be treated as such. Their great concern for the glory of God led them to take this step, which at first view might appear precipitate; but, that they might do nothing rashly, they first sent Phinehas and ten princes, one out of each tribe, to require an explanation of their motives in erecting this altar.

And they came unto the children of Reuben, and to the children of Gad, and to the half tribe of Manasseh, unto the land of Gilead,.... The deputation came thither; they either sent for the chiefs among the two tribes and a half, to meet them at some place, or they, having a notion of their coming, assembled together to receive them, and hear what they had to say to them:

and they spake with them, saying; as follows; very probably Phinehas was the mouth of the whole, for there could be but one speaker.

CONTENTION 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.