יהושע, פרק כ״ב, פסוק ל״ד

After constructing their altar, the tribes settling east of the Jordan River gave the structure a specific name to ensure its true purpose would never be misunderstood. The historical record notes this naming in a shortened manner, omitting the specific word they used. However, the primary approach among commentators is that the tribes called the altar "Witness" [רש״י, רד״ק, מצודת דוד, מנחת שי]. A slightly different perspective suggests the exact title given was the complete phrase, "For it is a witness" [ביאור שטיינזלץ].

Assigning this title was not a random decision; it perfectly expressed the exact reason the structure was built [מלבי״ם]. The altar was intended to serve as a living testament between the tribes living on the eastern side of the Jordan River and the rest of the Israelites on the western side.

This physical witness stood to declare the complete and shared faith of both parts of the nation, affirming together that God is the true God [מצודת דוד]. Naming the altar was a clear declaration that God is the one and only God, and that there is no other. Ultimately, it served as a binding promise for future generations that the eastern tribes would never exchange the worship of God for another deity, nor would they ever offer sacrifices on another altar [מלבי״ם, ביאור שטיינזלץ].