John Calvin Commentary Joshua 22:11

"And the children of Israel heard say, Behold, the children of Reuben and the children of Gad and the half-tribe of Manasseh have built an altar in the forefront of the land of Canaan, in the region about the Jordan, on the side that pertaineth to the children of Israel." — Joshua 22:11 (ASV)

And the children of Israel heard say, and so on. There is no doubt that they were inflamed with holy zeal, nor ought their vehemence to seem excessive in taking up arms to destroy their countrymen over a pile of stones. For they truly and wisely judged that the lawful sanctuary of God was polluted and His worship profaned, that sacred things were violated, religious unity destroyed, and a door opened for unrestrained superstitious practices, if sacrifices were offered to God in two places; for God had, for these reasons, so solemnly bound the whole people to a single altar. Not rashly, therefore, do the ten tribes, upon hearing of a profane altar, detest its sacrilegious audacity.

Here, then, we have an illustrious display of piety, teaching us that if we see the pure worship of God corrupted, we must be vigorous, to the utmost of our ability, in vindicating it. The sword, indeed, has not been committed into the hands of all; but each person must, according to their calling and office, strive resolutely and firmly to maintain the purity of religion against all corruptions.

Especially deserving of the highest praise was the zeal of the half-tribe of Manasseh, who, setting aside all natural family ties, did not spare their own relatives. I admit, however, that this zeal, though pious, was not free from turbulent impetuosity, since they rushed to declare war before they inquired about their brothers' intentions and had properly ascertained the facts of the situation. War, I admit, was declared only conditionally, for they sent ambassadors to report back after they had carefully investigated the matter, and they took no action to inflict punishment until they were certified of the crime's existence. Therefore, an excuse may be made for their passionate fervor, as they prepared for battle in case any defection was discovered.