The Medrash writes on the passuk Aicha 1,5 קרא עלי מועד Hashem called an assembly to crush my young men. However there are sefarim such as the Ohaiv Yisrael who interpret this to mean that Yisrael did not possess a greater Yom Tov than Tisha B'av. How are we to understand this description of Tisha B'av, a day of national tragedy and mourning for already close to 20 centuries, and yet still be deemed as a special time of joy?

Another question that begs an answer is the gemarah in Yuma 54b which states that when the Romans entered the Beis Hamikdash they saw that the angel figurines on the Aron were hugging each other
אמר ריש לקיש בשעה שנכנסו נכרים להיכל ראו כרובים המעורין זה בזה
This description is very perplexing. The gemarah in Baba Basra 99 explains the miracle of the cherubim as follows. When Yisrael possessed an intimate relationship with Hashem by observing the Torah and mitzvos, the cherubim faced each other. However, when they were spiritual dysfunctional they did not. If so how could it be that at the time that the Beis Hamikdash was being destroyed because of Am Yisrael's wayward relationship with Hashem, they were found embracing each other which is an expression of love?

To answer both difficulties we will bring an explanation of Rav Dessler ztl concerning the breaking of the Luchos. Upon seeing Yisrael's rebellion against Hashem by worshipping the Aigel, Moshe broke the Luchos. Hashem's response was אשר שברת which Chazal interpret this to mean יישר כח may your strength continue to be straight. In other words Hashem thanked Moshe for his deliberate destructive action. In explaining this Chazal, Rav Dessler elaborates on the fundamental relationship between light and energy flow and the vessel that is waiting to receive them. When Hashem reveals a spiritual force of light there must be a vessel worthy and capable of receiving it without being destroyed. If the vessel is incompatible with the revelation, then there are two available choices. One is to remove the vessel and preserve the light or to remove the light and preserve the vessel. When Moshe descended from Har Sinai with the Luchos, he was bringing to Am Yisrael a lofty celestial light to change for the better Man and the world. By worshipping the Aigel Yisrael became unworthy and incompatible to receive it and the shidduch between the two terminated. Moshe then made the decisive choice to remove the light rather than to annihilate Am Yisrael's existence. This selection of Moshe was greatly applauded by Hashem with the words יישר כחך. For by doing so, he eliminated from Hashem to decide on Yisrael's destruction amidst all the prosecution forces and kitrugim that were aroused because Yisrael's blatant avodah zara.

Let us employ this same reasoning in the destruction of the Beis Hamikdash. It was the residing place of Hashem's Shechinah within Am Yisrael. When we were no more worthy for this merit on account of our aveiros, two possible events could have been triggered. One was the destruction of the Beis Hamikdash and the exile of the Jewish Nation, or the annihilation of Am Yisrael once in for all. This time it was Hashem who made the decision and His choice was to obliterate the Beis Hamikdash instead and thereby send Yisrael into galus as a tikkun and atonement. This is the explanation of the Chazal that says Aicha Rabbasi 4,15שפך חמתו על עצים ואבנים He poured His anger on wood and stones.
רש"י קידושין לא:
מזמור לאסף אלהים באו גוים בנחלתך וגו' קינה לאסף מיבעי ליה? ודרש כך שאמר אסף שירה על שכילה הקב"ה חמתו בעצים ואבנים שבביתו ומתוך כך הותיר פליטה בישראל שאלמלא כך לא נשתייר משונאי ישראל שריד וכן הוא אומר כלה ה' את חמתו ויצת אש בציון (איכה ד) ילקוט שמעוני תהלים עט.

A song composed by Asaf Elokim the goyim entered Your Mikdash and destroyed it. Shouldn't he have changed the word of מזמור to קינה and איכה? But rather Hashem let out his anger by burning down the Beis Hamikdash its wood and stones. The words of כילה חמתו is gematriah יישר . The same יישר כח that Hashem gave to Moshe for breaking the Luchos was also hinted in the destruction of the Beis Hamikdash in the place of Am Yisrael.

The passuk says Aicha 1,8 חטא חטאה ירושלים על כן לנידה היתה Yisrael did an accidental sin therefore she is put into excommunication and galus. The Bnei Yissaschor asks that the word חטאdescribes a שוגג an involuntary aveirah. Yet we know that before the destruction of the Mikdash they were warned by the Neviim of the impending destruction which describes their aveiros to an intentional? He answers that since every Yid has a spark of kedusha and tahara that embodies his essence, his deep nature doesn't really want to do the aveirah. Therefore the Beis Hamikdash was destroyed and not Am Yisrael. This is the reason why the passuk portrays Am Yisrael as Nidah נדה which is not necessarily to be interpreted as excommunication but rather a woman who is tamei because of her menstruation. True, she is prohibited to have relations during her period of tumah but she will soon purify herself and will be once again permitted to live with her husband. This back and forth relationship being permitted and times of prohibition only applies by the Niddah and not with other עריות who are forbidden forever. על כן לנדה היתה

This interpretation of the Bnei Yissaschor is hinted in Sanhedrin 110b

(דברים כט כז) וישליכם אל ארץ אחרת כיום הזה מה היום חוזר ומאיר אף ישראל כן

This could have been the kavanah of Yaakov when he bought the birthright of Aisav and said .מכרה כיום את בכורתך לי the word כיום was added to send the message to Aisav that even if he will renege on the sale and destroy our Beis Hamikdash he will never be able to destroy Am Yisrael for they are כיום like the day, that after the night the day returns.

With this interpretation we can now understand how the cherubim were found in an embrace position when the enemy entered the Mikdash. Even at the time of Yisrael's destruction, Hashem demonstrated to His nation the silver lining that lies hidden beneath the tragedy, that of נצח ישראל לא ישקר (Shmuel 1,15,29) that we will always remain Hashem's eternal people. By pouring His anger on the wood and stone Hashem was proclaiming that there is a טהרה a purity deep within us that can never be removed and which bonds us with an eternal relationship to Hashem. טהרה is gematriah עץ ואבן which supports this concept.

Furthermore the passuk says שובה ישראל עד ה' אלקיך . The reason why teshuvah is possible is because we find by both the luchos and the destruction of the Beis Hasmikdash the derech of tikkun Am Yisrael and not its destruction even though we transgressed the Three Cardinal Sins. That is hinted in the word שובה which is gematriah עצים אבנים. This might be part of the reason why it is a minhag that some people sleep on the ground; others sleep without a pillow; and still others place a stone beneath their heads on Tisha B'av. The purpose being in order to stir within us the silver lining of our continued existence and that is because Hashem took out His anger on the stones of the Mikdash and not on us.

Now we can understand why Tisha B'av is called a מועד a holiday. The fact that he Beis Hamikdash was destroyed instead of Am Yisrael is an eternal silver lining that Hashem demonstrated to Am Yisrael and to which we must rejoice about even though it was a tragedy. An allusion to this interpretation is the gematriah of מועד is also ויפדך He redeemed you