Joshua 12:2

Sihon king of the Amorites, who dwelt in Heshbon
Which he took from the Moabites, and made his capital city, ( Numbers 21:26 ) ;

[and] ruled from Aroer, which [is] upon the bank of the river of Arnon;
a city of Moab, which never fell into the hands of Sihon, and therefore he is said to rule from it but not over it:

and from the middle of the river;
that is, the river Arnon, which being the boundary of the Moabites and Amorites, the king of the Amorites might be said to rule from the middle of it:

and from half Gilead even unto the river Jabbok, [which is] the border
of the children of Ammon;
so it is said to be, ( Deuteronomy 3:16 ) ; it should be rendered, not "from half Gilead", but "and half Gilead", as it is in the Hebrew text, and so in the Targum; for half Gilead belonged to the kingdom of Sihon, as the other half did to the kingdom of Og, as in ( Joshua 12:5 ) ; and so Jarchi remarks.