On the three Shabbatot preceding Tisha B’Ab, we read special Haftarot called the "Telat De’puranuta" ("three of calamity") that record the prophets’ warnings of the impending destruction of the Temple and Jerusalem. On the seven Shabbatot following Tisha B’Ab, we read special Haftarot called "Sheb De’nehamata" ("seven of consolation") which foresee the redemption of the Jewish people and the rebuilding of the Temple and Jerusalem.
Some have suggested a possible allusion to this Halacha in the Torah itself. In the Book of Bereshit (15:19), God makes a promise to Abraham Abinu that his offspring will one day take possession of the lands of ten nations, and He then proceeds to list those ten nations. As Rashi notes, however, when Beneh Yisrael conquered the Land of Israel in the time of Yehoshua, they dispossessed only seven nations, not ten. Rashi explains that the three nations of Keni, Kenizi and Kadmoni, which were included among the ten nations in God’s list, are actually the nations of Amon, Moab and Edom. As we know, Beneh Yisrael did not take possession of these lands during the time of Yehoshua. Instead, Rashi comments, these countries will come under Jewish control only in the future, during the time of Mashiah. Thus, God’s promise to Abraham was fulfilled only partially during the time of Yehoshua – when Beneh Yisrael captured the land of seven nations – and it will be fully realized in the Messianic era.
It has been noted that this division between the seven nations and the three nations might perhaps correspond to the three Haftarot of calamity and the seven Haftarot of consolation. The seven Haftarot of hope and consolation parallel the seven kingdoms over which Beneh Yisrael have already seized control. The three Haftarot of calamity, by contrast, correspond to the three lands that we will possess only at the time of the final redemption. These three Haftarot speak of our current state of mourning and destruction, but, as is the case regarding the lands of Amon, Moab and Edom, their status will change in the future, when these weeks will, please God, be transformed into a period of great joy and celebration.