Deuteronomy 33:21

He provideth the first part for himself The first-fruits of the land of promise, the country of Sion, which was first conquered, and which he is said to provide for himself, because he asked and obtained it of Moses, and was the first who viewed his portion in the promised land. There, in a portion of the lawgiver, &c. This is obscurely expressed, but the meaning seems to be, he was there settled in a portion or settlement allotted him by Moses the Jewish legislator himself, whereas the portions beyond Jordan were given to the several tribes by Joshua, according to the direction of the lot. Or perhaps this part of the land is termed a portion of the lawgiver, because, lying beyond Jordan, it was the only part which Moses was permitted to enter upon. Was he seated Hebrew, ספון, sapun, covered, or protected: for their wives and children were secured in their cities, while many of the men went over to the war in Canaan. He came with the heads of the people, &c. Or with the princes, captains, or rulers of the people; that is, under their command and conduct. Or, as ראשׁי, roshee, may be understood, with the first, or in the front of the people, as the Syriac renders it; for this tribe and their brethren, whose lot fell beyond Jordan, were to march into Canaan before their brethren. Thus, again, he speaks, in the prophetic style, of a thing as already done, because he foresaw it would be done. He executed the justice of the Lord Or his just judgment against the Canaanites, as the rest of the Israelites did.