Deuteronomy 33:21

The first part - The first fruits of the land of promise, the country of Sihon, which was first conquered, which he is said to provide for himself, because he desired and obtained it of Moses. Of the law - giver - Of Moses, whose portion this is called, either because this part of the land beyond Jordan was the only part of the land which Moses was permitted to enter upon: or because it was given him by Moses, whereas the portions beyond Jordan were given to the several tribes by Joshua according to the direction of the lot. Seated - Heb. hid or protected: for their wives and children were secured in their cities, while many of their men went over to the war in Canaan. He came - He went, or he will go, to the war in Canaan, with the princes, or captains, or rulers of the people of Israel, that is, under their command and conduct, as indeed they did; or with the first of the people; or, in the front of the people, as the Syriack renders it; for this tribe and their brethren whose lot fell beyond Jordan, were to march into Canaan before their brethren. He executed - The just judgment of God against the Canaanites, as the rest of the Israelites did.