Because the enemy hath said - The Idumeans thought they would shortly be put in possession of all the strong places of Israel; the ancient high places shall be ours.
Matthew Henry
Concise Bible Commentary
Those who put contempt and reproach on God's people, will have them turned on themselves. God promises favour to his Israel. We have no reason to complain, if the more unkind men are, the more kind God is. They shall come again to their own border. It was a type of the heavenly Canaan, of which all God's children are heirs, and into which they all shall be brought together. And when God returns in mercy to a people who return to him in duty, all their grievances will be set right. The full completion of this prophecy must be in some future event.
SDA Bible Commentary (limited)
Volume 1-7
2. Ancient high places.Heb.bamoth ‘olam, an expression similar to the gib‘oth ‘olam, “everlasting hills,” of Gen. 49:26 and Deut. 33:15. The expression is doubtless synonymous with the “mountains of Israel.” The LXX reads “everlasting desolation,” as if the Hebrew read shimemoth ‘olam.