Twenty-one verses against one neighbour. The shortest book in the Hebrew Bible is a single sustained accusation of betrayal, and the betrayal it describes has a date — if the accusation is the one it appears to be.
What the book is
Obadiah is a single oracle against Edom, the kingdom south-east of the Dead Sea, traditionally descended from Esau and therefore Israel’s brother nation. The charge is specific: that Edom stood by while Jerusalem was sacked, gloated over it, looted, and handed over survivors.
There is no biography of the prophet, no call scene, and no date formula. The book is one chapter long.
How it is put together
The first section announces Edom’s fall — its rock strongholds will not save it, its allies will turn on it. The middle section states the charge, in a series of prohibitions cast in the past: you should not have looked on, should not have entered the gate, should not have handed over the fugitives. The close widens into judgement on the nations and restoration for Israel.
Verses 1 to 9 overlap substantially with Jeremiah 49:7–22, in places word for word. Either one drew on the other or both drew on a common source; the direction of dependence is argued and unresolved.
The dating question
The natural reading is that the disaster referred to is the Babylonian destruction of Jerusalem in 587 BCE, which gives a floor. On that reading Obadiah belongs to the sixth century, close enough to the event for the grievance to be raw.
The main alternative places it after an earlier sack — the Edomite and Philistine raids referred to in Chronicles, or the campaign of Shishak — which would push it several centuries earlier. Those readings have to explain why the language matches the sixth-century disaster so closely.
The honest position: 587 BCE is the strongest anchor available, and it anchors the grievance rather than the composition. A text can carry an old grievance.
Where the external record touches it
Edom itself is well attested. Assyrian records name Edomite kings paying tribute from the eighth century onward, and Edomite settlement, pottery and script are documented archaeologically in the southern Levant and in the Negev.
The Arad ostraca, a group of Hebrew military letters from a Judahite fortress, include an order to send men to Ramat-Negev against an Edomite threat — a contemporary Judahite document treating Edom as a hostile pressure on Judah’s southern border in the last years of the kingdom. That is not confirmation of Obadiah’s charge, but it is independent evidence of the situation the charge assumes.
What happened to Edom afterwards is documented in outline. Edomite territory was progressively occupied, Edomite population moved west into what became Idumaea, and the Nabataeans took over the old heartland. The book’s announcement that Edom would be dispossessed corresponds to an actual displacement; the question of whether the text precedes it is the same dating question as before, and it is not resolved by the outcome.
Related: the overviews of Jeremiah, whose chapter 49 carries the parallel oracle, and Lamentations, on the disaster Obadiah refers to.