Numbers 24:18

And Edom shall be a possession, Seir also shall be a possession for his enemies; and Israel shall do valiantly.

The verse belongs to Balaam's unwilling prophecy of blessing upon Israel concerning Israel's triumph and prevailing. It was uttered in the setting where Balak moved Balaam from place to place in the vain hope of turning that blessing into a curse. It stands as poetry and song in the form of a blessing on Israel.

Edom and Seir, also called Mount Seir, are destined to become a possession for enemies, while Israel will act with courage and win triumphantly. The surrounding prophecy foretells a ruler arising from Jacob, that is from Israel, who will have dominion.

It points to Israel's future victories and settlement in the land after conquering the Canaanites, so that attempts to subdue Israel would fail. The Moabites understood it in this way, that Israel would conquer its enemies and settle in their land. It foretells the final and complete destruction of God's enemies, namely Moab and Edom. In a differing reading held in one place, Israel itself will triumph over Edom and take possession of its territory, including Seir.