Jabbok: A Stream on the East of the Jordan River, the Northern Boundary of the Possessions of the Ammonites
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Numbers 21:24
And Israel put him to the sword and took possession of his land, from the Arnon to the Jabbok—but only up to the border of the Ammonites, because it was fortified.
Judges 11:13
The king of the Ammonites answered Jephthah’s messengers, “When Israel came up out of Egypt, they seized my land, from the Arnon to the Jabbok and all the way to the Jordan. Now, therefore, restore it peaceably.”