Rabbah
Rabbah, also called Rabbath, is the royal city of the sons of Ammon east of the Jordan, fixed in scripture as the Ammonite capital, the depository for Og's iron bedstead, the prize of David's eastern campaign, and the recurring target of the prophets' oracles against Ammon. A second, distinct Rabbah is also listed among the hill-country towns of Judah.
The Ammonite Royal City
The first scripture-glimpse of Rabbah locates it as a fixed eastern landmark on the Israelite side of the Jordan. The Gadite border runs through Jazer, the cities of Gilead, and "half the land of the sons of Ammon, to Aroer that is before Rabbah" (Jos 13:25) — Aroer, on the edge of the allotment, is identified by its position directly opposite the Ammonite city.
Rabbah's standing as the Ammonite seat is reinforced by its role as a public memorial to the giant-king of Bashan. After the parenthetical notice that "only Og king of Bashan remained of the remnant of the Rephaim," the text points to the surviving relic: "look, his bedstead was a bedstead of iron; is it not in Rabbah of the sons of Ammon? Nine cubits was its length, and four cubits the width of it, after the cubit of a man" (De 3:11). The rhetorical "is it not" assumes the reader can be referred to Rabbah as the public custodian of the iron-bedstead.
The Siege under David
The long Davidic campaign against Ammon centers on Rabbah. Its opening notice doubles as the off-stage backdrop of David's Jerusalem-rooftop sin: "at the return of the year, at the time when kings go out [to battle], that David sent Joab, and his slaves with him, and all Israel; and they destroyed the sons of Ammon, and besieged Rabbah. But David tarried at Jerusalem" (2Sa 11:1).
The siege closes when Joab forces the issue. "Now Joab fought against Rabbah of the sons of Ammon, and took the royal city" (2Sa 12:26), and at once sends to David: "I have fought against Rabbah; yes, I have taken the city of waters. Now therefore gather the rest of the people together, and encamp against the city, and take it; or else I will take the city, and it will be called after my name" (2Sa 12:27-28). David obliges, gathering the people, going to Rabbah, fighting against it, and taking it (2Sa 12:29). The spoil is dramatic: "he took the crown of Milcom from off his head; and its weight was a talent of gold, and [in it were] precious stones; and it was set on David's head. And he brought forth the spoil of the city, exceedingly much" (2Sa 12:30). The Ammonite population is then put under conscription "with saws, and with harrows of iron, and with axes of iron," made to "serve making bricks," and the same is done "to all the cities of the sons of Ammon" before David and the people return to Jerusalem (2Sa 12:31).
The Chronicler reports the same campaign in compact form. "It came to pass, at the time of the return of the year, at the time when kings go out [to battle], that Joab led forth the army, and wasted the country of the sons of Ammon, and came and besieged Rabbah. But David tarried at Jerusalem. And Joab struck Rabbah, and overthrew it" (1Ch 20:1). The Milcom-crown of "a talent of gold" with "precious stones in it" is again set on David's head, and again the Ammonite population is put to saws, harrows of iron, and axes, and the same is done "to all the cities of the sons of Ammon" before the army returns to Jerusalem (1Ch 20:2-3).
Prophesied Against
Once Rabbah falls back into Ammonite hands, the prophets repeatedly mark it out for judgement. Jeremiah delivers a Yahweh-oracle that names the city: "Therefore, look, the days come, says Yahweh, that I will cause an alarm of war to be heard against Rabbah of the sons of Ammon; and it will become a desolate heap, and her daughters will be burned with fire: then will Israel possess those who possessed him, says Yahweh" (Jer 49:2). The lament extends to its dependent towns and people: "Wail, O Heshbon, for Ai is laid waste; cry, you⁺ daughters of Rabbah, gird⁺ with sackcloth: lament, and run to and fro among the fences; for Milcom will go into captivity, his priests and his princes together" (Jer 49:3).
Ezekiel sets Rabbah at the end of one of the two roads of Nebuchadnezzar's divination-sign: "You will appoint a way for the sword to come to Rabbah of the sons of Ammon, and to Judah in Jerusalem the fortified" (Eze 21:20) — Rabbah is paired with Jerusalem as a comparable fortified target of the same sword. A later Ezekiel oracle reduces the city's status to an open pasture: "I will make Rabbah a stable for camels, and the sons of Ammon a couching-place for flocks: and you⁺ will know that I am Yahweh" (Eze 25:5).
Amos closes the same arc by aiming the judgement-fire of his Ammon oracle at Rabbah's defences: "But I will kindle a fire in the wall of Rabbah, and it will devour its palaces, with shouting in the day of battle, with a tempest in the day of the whirlwind" (Am 1:14).
Rabbah of Judah
A second, distinct Rabbah sits within the inheritance of the tribe of Judah. The hill-country town-list closes with "Kiriath-baal (the same is Kiriath-jearim), and Rabbah; two cities with their villages" (Jos 15:60). This Judahite Rabbah is named once and then drops from the narrative; the rest of the scripture-record of "Rabbah" is the Ammonite royal city.