Shemot (Exodus) 32:23-25 – Aaron recounts to Moshe the events leading up to the golden Calf.
Bamidbar (Numbers) 13:32, 14:1, 14:34 – The spies publicly reported that the land promised to them by Hashem was not worth entering, and any attempt to conquer it would fail.
Ashes to Ashes; Dust to Dust
Zechariah 8:19 – There are four fasts that commemorate the destruction, which will be turned into days of joy when the Temple is rebuilt.
Mishnah, Ta’anit 4:6 – The five calamities of Tishah B’Av focus on the destruction of the Temple and Jewish settlement in the land of Israel
1. It was decreed upon our ancestors not to enter the Land.
2. The First Temple was destroyed.
3. The Second Temple was destroyed.
4. The city of Beitar was captured.
5. Jerusalem was "plowed" over.
The Power of A Good Cry
Rabbi Eliyahu Kitov, Sefer HaToda’ah, Ch. 33 – Mourning for past mistakes helps guarantee a future.