Numbers 21:15

15 And he has appointed brooks to cause Er to dwell ; and it lies near to the coasts of Moab.

Numbers 21:15 Meaning and Commentary

Numbers 21:15

And at the stream of the brooks that goeth down to the
dwelling of Ar
All that part of the country which lay upon the stream, as far as the city of Ar, the metropolis of Moab, called Ar of Moab, ( Isaiah 15:1 ) ,

and lieth upon the border of Moab;
as that city did; so far goes the quotation out of the aforesaid book, as a proof of what was taken by the Amorites from the Moabites, and were not in their possession when Israel were upon their borders; and therefore, in taking them from the Amorites, did no wrong to Moab.

Numbers 21:15 In-Context

13 And they departed thence and encamped on the other side of Arnon in the wilderness, which extends from the coasts of the Amorites; for Arnon is the borders of Moab, between Moab and the Amorites.
14 Therefore it is said in a book, A war of the Lord has set on fire Zoob, and the brooks of Arnon.
15 And he has appointed brooks to cause Er to dwell ; and it lies near to the coasts of Moab.
16 And thence the well; this the well of which the Lord said to Moses, Gather the people, and I will give them water to drink.
17 Then Israel sang this song at the well, Begin of the well;

The Brenton translation of the Septuagint is in the public domain.