Thou art to pass over through Ar,.... That is, over the river Arnon, by the city Ar of Moab, which was situated by it; see Deuteronomy 2:9 and so Moses and the people of Israel were to pass along by that:

and by the coast of Moab; for they were not admitted to enter the land and pass through it; only to travel on the borders of it, and that they were to begin to do this day; the day the Lord spake to Moses.

Thou art to pass over through Ar, the coast of Moab, this day:

2:8-23 We have the origin of the Moabites, Edomites, and Ammonites. Moses also gives an instance older than any of these; the Caphtorims drove the Avims out of their country. These revolutions show what uncertain things wordly possessions are. It was so of old, and ever will be so. Families decline, and from them estates are transferred to families that increase; so little continuance is there in these things. This is recorded to encourage the children of Israel. If the providence of God has done this for Moabites and Ammonites, much more would his promise do it for Israel, his peculiar people. Cautions are given not to meddle with Moabites and Ammonites. Even wicked men must not be wronged. God gives and preserves outward blessings to wicked men; these are not the best things, he has better in store for his own children.