In the haftorah of Shabbos Nachamu, the navi Yeshaya is commanded to offer words of comfort to Klal Yisroel on the loss of the Beis HaMikdash and the suffering they have endured in exile. But the message he gives them does not seem to be one of consolation. First, he is asked to proclaim, "All flesh is like grass...Grass withers and blossoms fade, but the word of G-d stands forever" (40:6-8). Then the pesukim describe Hashem's greatness. "Who measured the waters in His palm; who arranged the heavens?... From whom did He seek counsel; who gave Him insight?... It is He who sits on top of the earth, with its inhabitants like grasshoppers... It is He who turns leaders into nothingness... If He were just to blow on them, they would wither (40:12-24)." And then the haftorah concludes, "Lift your eyes and see Who created these things (the heavenly bodies); He calls to each of them by name; by the abundance of His power and by the vigor of His strength, not one is missing. (40:26)" What is the navi's message? And how is it a source of comfort?
The Mishna (Ta'anis 4:8) quotes the statement of R' Shimon ben Gamliel, "The Jewish people never had such joyful days as Yom Kippur and Tu B'Av (the fifteenth of Av); on these days, the girls of Yerushalayim would go out with beautiful borrowed linen garments so as not to embarrass those who did not have (and young suitors would come to make matches with them)." The Gemara (30a) asks: what is so special about Tu B'Av? It is understandable why Yom Kippur should be singled out as an exceptionally joyous day of the year because it is the day that we are cleansed from our sins and we get to start fresh with a clean slate. But what is so special about Tu B'Av? And what is its connection to Yom Kippur?
The Gemara gives several answers to explain what exactly happened on Tu B'Av. The first answer is that Tu B'Av is the day that the different shevatim were allowed to intermarry with each other. The Torah at the end of Parshas Masei (36:6-9) describes how the daughters of Tzlafchad, who received their father's portion in Eretz Yisrael, were told they could marry only men from their own shevet Menashe so that their land would not pass to a different shevet. This caused a certain sense of estrangement in Klal Yisrael.
On Tu B'Av, a source was found which indicated that after the generation of the midbar, the intermarriage of the different shevatim should be permitted. This brought great joy to Klal Yisrael because now even a girl who inherited land from her father could marry a man from a different shevet. But it also took sacrifice on the part of the shevatim, because with this change, they were opening themselves up to the possibility that they might lose some of the land that had previously belonged to their shevet. That is why Tu B'Av is such a special yom tov, because it commemorates not only the reunification of Klal Yisrael, but the ability of the shevatim to sacrifice their own interests for the benefit a young girl's shidduch prospects.
What is the connection of Tu B'Av to Yom Kippur? The answer is that what makes Yom Kippur such a joyous day on the Jewish calendar is not simply the fact that we are forgiven on that day, but rather, that by neglecting our physical needs and our own self-importance on Yom Kippur, we are able to more fully appreciate the value of the people around us. As we say in the piyut after the avodah, Yom Kippur is "a day for increasing love and friendship, a day for abandoning jealousy and competition." It is a day to reorder our sense of priorities, to think less of our own interests and more of the interests of our fellow Jews. By fasting, we separate from physicality, and that allows us to acquire a more appropriate perspective on life.
This idea can give new meaning to the rest of the Mishna as well. The tanna describes how the young Jewish girls would go out on their shidduch quest wearing borrowed fancy clothing so as not to embarrass those who could not afford their own. Why mention this point? It certainly adds a sweet dimension to the story. But is there some deeper message? The tanna might be alluding to the fact that this kind of behavior - showing sensitivity for others - is especially appropriate on Yom Kippur and Tu B'Av because these are days when we remember how important it is to be caring of others even when that caring comes with sacrifice. And that is precisely what the wealthy girls were doing, because by sharing their garments, they were leveling the playing field for everyone and seemingly putting themselves at a disadvantage.
This might be the deeper meaning behind the statement of the Mishna that there was no greater yom tov for Klal Yisrael than Tu B'Av. Chazal tell us that the second Beis HaMikdash was destroyed because of sinas chinam - baseless hatred (Yoma 9b). A person acts with hatred when he is self-centered, when he is not willing to put himself in someone else's shoes and see things from the other person's perspective. The young girls who lent their clothes to their poor friends demonstrated that they understood the importance of thinking about someone else. Perhaps this is what the tanna meant to say, that what made Tu B'Av such a special yom tov is the very fact that the young girls cared so much about each other. What a fitting response to the sinas chinam which brought us the mourning of Tisha B'Av in the first place!
How does a person learn to think and care about others? One way is by developing a sense of humility. When a person appreciates that every individual is special because each one of us has a unique role to play in the world, there is no room for arrogance or competition. If we are all equal in Hashem's eyes, reaching out to others will not put us at a disadvantage because Hashem will ensure that we receive exactly what we deserve.
This is the message of consolation the navi shares with Klal Yisrael: the way to reconnect with the Ribbono Shel Olam is by developing a proper sense of self-worth. On the one hand, man is like withering grass compared to Hashem's omnipotence and grandeur. But at the same time, Hashem cares about each and every individual creation - "He calls to each of them by name." Since life is fleeting, we should not get involved in petty arguments and momentary pleasures. Each one of us has a mission to fulfill and we should not be distracted with trivial pursuits. Instead, we should try to serve Hakadosh Boruch Hu in everything we do and strengthen our relationship with Him. Moreover, we should never belittle someone else because in Hashem's eyes each one of us is special. By appreciating the value of each and every Jew, and living constantly with an awareness of the Ribbono Shel Olam, we draw closer to Him, and we can feel comforted by the knowledge that Hashem is as close to us as we allow Him to be.