Deuteronomy 2:31
And the LORD said unto me, Behold, I have begun to give Sihon and his land before thee: begin to possess, that thou mayest inherit his land. And the LORD said unto me, Behold, I have begun to give Sihon and his land before thee: begin to possess, that thou mayest inherit his land.
Israel turned northward toward the promised land after passing to the south of Edom, traveling over a vast elevated plain, crossing the brook Zered, and passing to the east of Moab and Ammon without distressing them in battle because God had given Ar and their land to the children of Lot for a possession. In that setting the Lord promised that He had begun to give Sihon and his land before Israel, bidding them begin to possess that they might inherit it. The promise was fulfilled when Israel crossed the river Arnon, attacked the Amorites, won the battle, and soon took possession of the country of the Amorites.
The victory was won because the Captain of the Lord's host fought for His people. That same power would have given Israel victory thirty-eight years earlier if Israel had trusted Him. Together with the rest of Deuteronomy 2, the verse presents the blessings of obedience and the warnings against disobedience. Its promises are to be read and repeated again and again.