Deuteronomy 2:24

Rise ye up, take your journey, and pass over the river Arnon,
&c.] Which was on the border of Moab, and divided between Moab and the Amorites, ( Numbers 21:13 )

behold, I have given into thy hand Sihon, the Amorite, king of Heshbon,
and his land; that is, he had determined to give it to the Israelites, for as yet it was not actually given; of this king, and the place he(See Gill on :) (See Gill on Numbers 21:26) begin to possess it, and contend with him in battle; provoke him to war, fight with him, take his land from him, and enter upon the possession of it, hereby assuring of victory.