Dora Bas Rivka Silver O'H
Ovadya (Obadiah) first appeared in I Kings 18. When Izevel (Queen Jezebel) was killing prophets, Obadiah hid 100 of them in caves at personal risk, for which he was rewarded with the gift of prophecy himself. Obadiah was also a convert from the nation of Edom, who were descendants of Jacob’s brother Esau. The Talmud (Sanhedrin 39b) says that Obadiah is like an axe whose handle is carved from one of those trees. The forest is brought down by something that came from within it.
The Edom of Obadiah's prophecy can refer to the Biblical nation of Edom and the first Temple era, to Rome and the second Temple (which was destroyed by the Romans), or to the Christian world in general. (If Edom means that, then the book would be prophesying an event in our future, presumably the war of Gog and Magog.)
G-d has sent a message about Edom. The nations will go to war against her; they consider her insignificant. (Rashi quotes the Talmud in Avodah Zarah 10a that the other nations looked down on Edom because they didn't have their own script or language.) Edom let the evil in her heart seduce her into speaking out against Israel. They "live in the cracks of the rocks of (their) high dwelling," meaning that Edom relies on the merits of our common ancestors, Abraham and Isaac, though that won't be enough to save them.
Edom is full of herself, asking "Who could possibly bring me back down to earth?" G-d says that even if they put their "nest" between the stars, He will bring them down from there. If burglars came by night, they would only rob until they had enough. This will not be the case with Edom, who will be picked clean by their enemies. Their allies will betray them.
What did Edom do to deserve this punishment? They oppressed their brother Jacob (Israel), either actively in the destruction of the Second Temple, or tacitly in the destruction of the first. Assuming we are speaking of the first Temple, they stood far off, offering no help against the Babylonians. If anything, they rejoiced in Israel's downfall and stretched out their hands to plunder their wealth. The day of G-d over all nations is close at hand; as Edom did to others will be done to them. Payback for their actions will be deposited on their heads.
On Mt. Zion there will be a refuge and it will be holy. (“It” could refer either to the mountain or to the group of people there.) Israel will inherit that which they inherited before, plus they will inherit from Edom, Moav and the Philistines. The house of Jacob will be fire, the house of Joseph will be flame and the house of Esau (Edom) will be like straw; they will be consumed. (Why is Joseph singled out? The Talmud in Baba Basra 123b says that only Joseph's descendants will be able to defeat Esau's descendants. If any other Tribe asked Edom, "Why did you persecute your brother?" they could reply "YOU persecuted YOUR brother!" Joseph, however, could say "I forgave my brothers for harming me, why don’t you forgive yours?")
There will be no survivor from Edom, for G-d has spoken. The people Israel will inherit the mountain of Esau, the Philistines, and other lands. The masses of Jews exiled as far as France and Spain will inherit the cities of the south. Saviors – possibly referring to Moshiach (the Messiah) and other great leaders of Jewish history – will ascend Mt. Zion to judge Edom. At that time, the whole world will recognize the kingship of G-d.