The mention of the Moabites gives occasion to the author to introduce some notices of the ancient inhabitants of Edom and Moab. In Moab dwelt, in the earlier times, the Emim, a giant race, potent and numerous, like the 'Anakim.
They were also, like the 'Anakim reckoned among the Rephaim, but were by the Moabites called Emim. The word Emim means frightful, and was given to these men probably because of their huge stature and fierce aspect.
Anakims (see Deuteronomy 1:28). Rephaim seems to have been a generic name of these gigantic Canaanitish tribes (see Genesis 14:5; Genesis 15:20). The Horim appear from the name (from חוֹד, a cave) to have been a Troglodyte race, inhabiting the caves which abound in the Edomite range, and with whom, perhaps, originated the conception which was at a later period carried out in the marvelous rock city of Petra.
Of their own origin nothing is known. As Israel did [or has done] unto the land of his possession. This cannot be regarded as uttered proleptically; it must either be the insertion of a later age, or it must refer to the conquest which had actually been made before this by the Israelites of the land to the east of the Jordan.
and which is, in Deuteronomy 3:20, described as the possession which the Lord had given to the two tribes and a half to whom it had been assigned. The latter is the preferable supposition.