The prophet Jeremiah who lived through the terrible time of the destruction of Jerusalem and the Beth Hamikdash, was in many respects like Moses, the "Father of the Prophets." Like Moses, Jeremiah prophesied for forty years. He, too, frequently faced danger and violence to his person. Moses was thrown into the water (in the Nile River) and Jeremiah into a pit; the former was saved by a maid (of Pharaoh's daughter), the latter by a slave. Both continually admonished the people to keep to the path of the Torah.
Jeremiah was a priest, but the cherished priestly privilege of blessing his people was not his only duty. He wanted only to bless his beloved people with the priestly benediction ("G-d bless you and keep the..."), yet it was his duty also to admonish the people and warn them of the terrible calamity of the Destruction of Jerusalem.
Why were the lamentations (in the Book of Echah, written by Jeremiah) composed in the order of the Hebrew Aleph-Beth? Because the Jewish people had forsaken the Torah (which is written in the Hebrew alphabet).
On Tisha b'Av the disciples of Ben Azzai came to him and said: "Master, tell us something about the Book of Echah."
Replied the sage: "Echah is spelled with an aleph (1), yud (10), chof (20) and hey (5). The very name of the book of Lamentations spells the reason for the destruction of our land and of our exile. Our people were driven from the Holy Land because they were disloyal to the One and Only G-d, broke the Ten Commandments, betrayed the Covenant of Circumcision which was given to Abraham our father in the 20th generation since the creation of the world, and did not observe the Five Books of Moses."
Said Rabbi Joshua ben Levi: "Since the day that G-d destroyed Jerusalem and the Beth Hamikdash, He knows of no joy. Only when Jerusalem and the Beth Hamikdash will be rebuilt, and the Jews will be restored as of old, will G-d rejoice again. May that day come speedily in our time. Amen."
--Talks and Tales