God having tried the self-denial of his people in forbidding them to meddle with the Moabites and Ammonites, and they having quietly passed by those rich countries, and, though superior in number, not made any attack upon them, here he recompenses them for their obedience by giving them possession of the country of Sihon king of the Amorites. If we forbear what God forbids, we shall receive what he promises, and shall be no losers at last by our obedience, though it may seem for the present to be to our loss. Wrong not others, and God shall right thee.
I. God gives them commission to seize upon the country of Sihon king of Heshbon, Deu 2:24, Deu 2:25. This was then God's way of disposing of kingdoms, but such particular grants are not now either to be expected or pretended. In this commission observe, 1. Though God assured them that the land should be their own, yet they must bestir themselves, and contend in battle with the enemy. What God gives we must endeavour to get. 2. God promises that when they fight he will fight for them. Do you begin to possess it, and I will begin to put the dread of you upon them. God would dispirit the enemy and so destroy them, would magnify Israel and so terrify all those against whom they were commissioned. See Exo 15:14.
II. Moses sends to Sihon a message of peace, and only begs a passage through his land, with a promise to give his country no disturbance, but the advantage of trading for ready money with so great a body, Deu 2:26-29. Moses herein did neither disobey God, who bade him contend with Sihon, nor dissemble with Sihon; but doubtless it was by divine direction that he did it, that Sihon might be left inexcusable, though God hardened his heart. This may illustrate the method of God's dealing with those to whom he gives his gospel, but does not give grace to believe it.
III. Sihon began the war (Deu 2:32), God having made his heart obstinate, and hidden from his eyes the thing that belonged to his peace (Deu 2:30), that he might deliver him into the hand of Israel. Those that meddle with the people of God meddle to their own hurt; and God sometimes ruins his enemies by their own resolves. See Mic 4:11-13; Rev 16:14.
IV. Israel was victorious. 1. They put all the Amorites to the sword, men, women, and children (Deu 2:33, Deu 2:34); this they did as the executioners of God's wrath; now the measure of the Amorites' iniquity was full (Gen 15:16), and the longer it was in the filling the sorer was the reckoning at last. This was one of the devoted nations. They died, not as Israel's enemies, but as sacrifices to divine justice, in the offering of which sacrifices Israel was employed, as a kingdom of priests. The case being therefore extraordinary, it ought not to be drawn into a precedent for military executions, which make no distinction and give no quarter: those will have judgment without mercy that show no mercy. 2. They took possession of all they had; their cities (Deu 2:34), their goods (Deu 2:35), and their land, Deu 2:36. The wealth of the sinner is laid up for the just. What a new world did Israel now come into! Most of them were born, and had lived all their days, in a vast howling wilderness, where they knew not what either fields or cities were, had no houses to dwell in, and neither sowed nor reaped; and now of a sudden to become masters of a country so well built, so well husbanded, this made them amends for their long waiting, and yet it was but the earnest of a great deal more. 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.

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, Num 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 Num 21:21, Num 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.

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 Deu 7:2; Deu 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 (Num 21:23; Jdg 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.

Next: Deuteronomy Chapter 3