And when they came unto the borders of Jordan, that are in the land of Canaan, the children of Reuben and the children of Gad and the half tribe of Manasseh built {f} there an altar by Jordan, a great altar to see to.

(f) That is, beyond Jordan: for sometime the whole country on both sides of Jordan is referred to as Canaan.

Wesley's Notes

22:10 Built an altar - About that time when they came to them, they designed it, and as soon as they were got over Jordan, which was in a very little time, they effected and perfected it. They built it, no doubt, on their own side of the water: for how could they build on other men's land, without their consent? And it is said, in the following verse , to be over against the land of Jordan. Nor would there have been cause to suspect that it was designed for sacrifice, if they had not built it among themselves.

Jamieson-Fausset-Brown Bible Commentary

Jos 22:10. They Build the Altar of Testimony on Their Journey.

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.

Matthew Henry's Concise Commentary

22:10-20 Here is the care of the separated tribes to keep their hold of Canaan's religion. At first sight it seemed a design to set up an altar against the altar at Shiloh. God is jealous for his own institutions; we should be so too, and afraid of every thing that looks like, or leads to idolatry. Corruptions in religion are best dealt with at first. But their prudence in following up this zealous resolution is no less commendable. Many an unhappy strife would be prevented, or soon made up, by inquiries into the matter of the offence. The remembrance of great sins committed formerly, should engage us to stand on our guard against the beginnings of sin; for the way of sin is down-hill. We are all concerned to reprove our neighbour when he does amiss, lest we suffer sin upon him, Le 19:17. The offer made that they should be welcome to come to the land where the Lord's tabernacle was, and settle there, was in the spirit of true Israelites.