Rise ye up, take your journey, and pass over the river Arnon,.... 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 was king of; see Gill on Numbers 21:21, 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.

The Help of God in the Conquest of the Kingdom of Sihon. - Deuteronomy 2:24. Whereas the Israelites were not to make war upon the kindred tribes of Edomites, Moabites, and Ammonites, or drive them out of the possessions given to them by God; the Lord had given the Amorites, who had forced as way into Gilead and Bashan, into their hands.

Deuteronomy 2:24-25

While they were encamped on the Arnon, the border of the Amoritish king of Sihon, He directed them to cross this frontier and take possession of the land of Sihon, and promised that He would give this king with all his territory into their hands, and that henceforward ("this day," the day on which Israel crossed the Arnon) He would put fear and terror of Israel upon all nations under the whole heaven, so that as soon as they heard the report of Israel they would tremble and writhe before them. רשׁ החל, "begin, take," an oratorical expression for "begin to take" (רשׁ in pause for רשׁ, Deuteronomy 1:21). The expression, "all nations under the whole heaven," is hyperbolical; it is not to be restricted, however, to the Canaanites and other neighbouring tribes, but, according to what follows, to be understood as referring to all nations to whom the report of the great deeds of the Lord upon and on behalf of Israel should reach (cf. Deuteronomy 11:25 and Exodus 23:27). אשׁר, so that (as in Genesis 11:7; Genesis 13:16; Genesis 22:14). וחלוּ, with the accent upon the last syllable, on account of the ו consec. (Ewald, 234, a.), from חוּל, to twist, or writhe with pain, here with anxiety.

Rise ye up, take your journey, and pass over the river Arnon: behold, I have given into thine hand Sihon the {k} Amorite, king of Heshbon, and his land: begin to possess it, and contend with him in battle.

(k) According to his promise made to Abraham, Ge 15:16.

begin...: Heb. begin, possess

24-36. Rise ye up . and pass over the river Arnon-At its mouth, this stream is eighty-two feet wide and four deep. It flows in a channel banked by perpendicular cliffs of sandstone. At the date of the Israelitish migration to the east of the Jordan, the whole of the fine country lying between the Arnon and the Jabbok including the mountainous tract of Gilead, had been seized by the Amorites, who, being one of the nations doomed to destruction (see De 7:2; 20:16), were utterly exterminated. Their country fell by right of conquest into the hands of the Israelites. Moses, however, considering this doom as referring solely to the Amorite possessions west of Jordan, sent a pacific message to Sihon, requesting permission to go through his territories, which lay on the east of that river. It is always customary to send messengers before to prepare the way; but the rejection of Moses' request by Sihon and his opposition to the advance of the Israelites (Nu 21:23; Jud 11:26) drew down on himself and his Amorite subjects the predicted doom on the first pitched battlefield with the Canaanites. It secured to Israel not only the possession of a fine and pastoral country, but, what was of more importance to them, a free access to the Jordan on the east.

2:24-37 God tried his people, by forbidding them to meddle with the rich countries of Moab and Ammon. He gives them possession of the country of the Amorites. If we keep from what God forbids, we shall not lose by our obedience. The earth is the Lord's and the fulness thereof; and he gives it to whom he pleases; but when there is no express direction, none can plead his grant for such proceedings. Though God assured the Israelites that the land should be their own, yet they must contend with the enemy. What God gives we must endeavour to get. What a new world did Israel now come into! Much more joyful will the change be, which holy souls will experience, when they remove out of the wilderness of this world to the better country, that is, the heavenly, to the city that has foundations. Let us, by reflecting upon God's dealings with his people Israel, be led to meditate upon our years spent in vanity, through our transgressions. But happy are those whom Jesus has delivered from the wrath to come. To whom he hath given the earnest of his Spirit in their hearts. Their inheritance cannot be affected by revolutions of kingdoms, or changes in earthly possessions.