Joshua 13:16
And their coast was from Aroer, that is on the bank of the river Arnon, and the city that is in the midst of the river, and all the plain by Medeba; And their coast was from Aroer, that is on the bank of the river Arnon, and the city that is in the midst of the river, and all the plain by Medeba;
The verse defines part of the boundary of the territory allotted to Reuben. That boundary is marked by Aroer on the bank of the Arnon, by the city lying in the midst of the river, and by the whole plain by Medeba. This description belongs to the geographical record of the distribution of the land, drawn from documents that accurately described the properties.