9th day of Av a great day of mourning and hope

Recall that, in Numbers 13 the Twelve Spies sent by Moses to observe the land of Canaan returned from their mission.

27 They gave their account to him and said, “We went into the land where you sent us. It IS flowing with milk and honey — this is some of its fruit. 28 Except, the people living in the land are powerful, and the cities are fortified and very large.” 32They spread among Bnei-Yisrael a bad report about the land they had explored…

Only two of the spies, Joshua and Caleb, brought a positive report, while the others spoke disparagingly about the land. The majority report caused B’nei Israel to cry, panic and despair of ever entering the "Promised Land".

For this, the Mishnah (Taanit 4:6) declares that they were punished by God and that their generation would not enter the land. The midrash further implies that God addressed the grumbling and disbelieving masses, saying "You cried before me pointlessly, I will fix for you [this day as a day of] crying for the generations." Tradition holds that the day that B’nei Israel rejected God’s gift of Canaan was on the 9th of Av, and that the date of Tisha B’Av has become, and continues to evolve as a Jewish day of Mourning for a host of tragedies which occurred on or near the 9th of Av.