When did Ovadyah prophesize?
Radak: This is not known. According to Chazal, this is Ovadyah who was with Achav. With the destruction of Edom will be the salvation of Yisrael. This Nevu'ah applies to Bayis Sheni, when Edom harmed Yisrael at the time of its Churban. At the end of days, Yisrael will ascend from exile. Eretz Edom nowadays is not for Bnei Edom; the nations were mixed up. Most of them follow the creed of the Notzrim or Yishmaelim. We do not know who is from Edom, Mo'av, Amon or other nations. All were exiled from their lands and mixed with other nations. However, Malchus Romi was initially mostly of Bnei Edom.
Malbim: Edom harmed Yisrael at the first Churban (they rejoiced over it) and at the second Churban, which was via Romi. Romi is called on Edom's name, for Bnei Edom settled in the city Romi, and afterwards their creed was based on Edom. Mahari brought proofs for this in Yeshayah (Perek 34). Also, Hordus brought Bnei Edom into the law of Yisrael via Milah and Tevilah, and they helped bring the Churban and became enemies. Afterwards, their creed spread, and all who follow it were called on Edom's name. Yisrael suffered under them exile and murders without number for many years. In the future, all members of that creed will gather to conquer Eretz Yisrael from the Yishmaelim, like is explained in Yechezkel's Nevu'ah of Gog and Magog (Perakim 32, 38-39). Then all Bnei Yishmael in the east will gather to take vengeance for their brothers.
Why did Ovadyah prophesize only about Edom?
Rashi citing Sanhedrin 39b: He was a convert from Edom. Hashem said, from them and among them I will bring on them 1 . Let, Ovadyah, who lived among two Resha'im (Achaz and Izevel), and did not learn from their deeds, come and punish (prophesize about the fall of the descendants of) Esav ha'Rasha, who lived among two Tzadikim (Yitzchak and Rivkah), and did not learn from their deeds.
Normally, a convert cannot receive Nevu'ah; 'the Shechinah rests only on families of proper lineage in Yisrael' (Kidushin 70b). Ovadyah received Nevu'ah only to enable an Edomi to prophesize the fall of Edom (refer to 1:1:2:1). (Heard from R. Meir Eliyahu Shilta, from Kabalah.)
Radak citing Pesachim 28a: This is like people say, the spoon that the craftsman made will burn his mouth with mustard!
Why does it say "l'Edom"?
Radak: This means Ba'avur (regarding) Edom, just like "Imri Li Achi Hu" (Bereishis 20:13).
Who heard from Hashem, and what did they hear?
Radak #1: The Goyim will say that they heard from Him that they will say to each other "let us rise against [Edom] in war"; it is as if "v'Tzir ba'Goyim Shalu'ach" (a Shali'ach was sent to arouse them to fight Edom).
Radak #2: Ovadyah says, I and other Nevi'im heard that Hashem said about Edom "v'Tzir ba'Goyim Shalu'ach." Also Yirmeyah (49:14) said so.
Malbim: Ovadyah says, I and some other Nevi'im heard [and prophesized] about the fall of Edom. Also Yirmeyah (49:14) said so.
What is the meaning of "v'Tzir ba'Goyim Shulach"?
Malbim: Messengers 1 will go among the Yishmaelim 2 to arouse each other "let us rise against [Edom] in war."
Metzudas Tziyon: Tzir is a Shali'ach, like "v'Tzir Emunim" (Mishlei 13:17).
The other Meforshim imply that Sheluchim will go around all the nations. (PF)
