Joshua 12:2

From the middle of the river: it is not unusual, even amongst us, for a river to be divided between two lords, and for their territories or jurisdictions to meet in the middle of the river; and besides, here is a very particular reason for this expression, because the city Ar, which was no part of Sihon’s dominions, but belonged to the Moabites, Deuteronomy 2:9,Deuteronomy 2:18, was in the middle of the river Arnon, Deuteronomy 2:36 Deuteronomy 3:16; and therefore the middle of the river is most fitly and properly here mentioned, as the bound of Sihon’s dominion on that side.

And from half Gilead, Heb. and the half Gilead, i.e. half of the country of Gilead: the particle from is not in the original, and this doth not seem to denote the term or bound from which his dominion begun, as our version implies, for so indeed it was not; but the place or country in and over which his dominion was, which, as is here said, began at Arnon, and took in half Gilead, and ended at Jabbok, beyond which was the other half of Gilead, which belonged to Og, as is expressly said, Joshua 12:5, where the words being wholly the same that are here, it is most reasonable to understand and translate them in the same manner.