World as a reward for Koresh because he cried and mourned when the goyim destroyed the Beis HaMikdash. According to the Chofetz Chaim’s zt'l calculation, Koresh was seven years old at the time of the Churban. A child of seven doesn't fully understand the devastation of the Churban. Nevertheless, he cried, and he was rewarded for his tears. How great will be the reward for the Yidden who mourn and weep for Yerushalayim!
Psikta d'Rav Kahana (ch.25) writes that Hashem swears, "Whoever waits for My kingdom [which will be revealed when Moshiach comes] I will testify for him for his benefit."
Mourning
It states (Divrei HaYamim 1, 16:27) במקומו וחדוה עוז, "Might and joy are in His place." Hashem resides in a place of joy. The Chasam Sofer zt'l (Drashos 7th of Av, 5560, p.307) writes that Tisha b'Av is an exception. Hashem mourns and cries on this day, and we should mourn and cry together with Him. "Hashem resides with joy, and Chazal say that Hashem doesn't reside in places where there is sadness. Nevertheless, Tisha b'Av is called מר יום, a bitter day. Therefore, it is proper for all the bitter and broken people to cry and mourn on this day when Hashem is also mourning. If they do so, their mourning will go up to a very high place. Although they don’t see it, their mazal sees, and they will hear the voice of Hashem crying together with them... Chazal say, 'In every generation, one must consider himself as if he was exiled from Yerushalayim.' This year's mourning shouldn't be the same as last year's and years before it. Each year has its unique set of distress and challenges we should mourn. This is as it states in the Kinos (#24) בית חורבן על חדש מספד שנה כל אספוד ...המקדש, "For the Churban Beis HaMikdash... I will mourn and eulogize each year anew."
Rebbe Pinchas Koritzer zt'l (Imrei Pinchas 378, 380) writes, "On this day, keviyachol, Hashem is crying. Therefore, when a person is also at this place [of mourning], he is protected [because he is with Hashem]. Laughing on Tisha b'Av is נפשות סכנת, dangerous because when one is with the king, he is protected, but when he is distant from the king, he doesn't have protection. And on this day, the Shechinah is keviyachol sitting on the earth [and the only way to connect and be with Hashem is through mourning]."
The Avodas Yisrael (Avos 3:1) describes the avodah of the Three Weeks and Tisha b'Av with a mashal: A father dropped diamonds into the garbage and asked his son to search the trash, find them, and clean them. It was a challenging and repulsive job. The son certainly would receive a great reward for doing this for his father, more significant than if he would serve his father in other ways. This describes the avodah of the Three Weeks and Tisha b'Av. It is a low time, a difficult period, but the avodah is very precious. The Avodas Yisrael concludes, "What a person can rectify on Tisha b'Av, which is a low day, he cannot rectify even on Simchas Torah."
Surprisingly, Shulchan Aruch (559:4) states, "We don't say tachanun or selichos on Tisha b'Av because it is called moed, a holiday." It states (Eichah 1:15) מועד עלי קרא, that Tisha b'Av is a moed, a holiday. The question is, how can Tisha b'Av be called a holiday?
Reb Mordechai Gifter zt'l answers (quoting his Rebbe, hy'd) that מועד means a gathering place (like מועד אהל). Yomim tovim are called Moed because on yom tov, we gather and connect with Hashem through joy. Tisha b'Av is called moed, because we connect to Hashem through our mourning.
On Tisha b'Av, we read איכה מגילת, and the word איכה is repeated at the beginning of many of its chapters. Furthermore, many of the kinos that we say on Tisha b'Av begin with the word ָהֵיכא. In the Torah, Hashem asks Adam HaRishon, ַיֶּכָּהא, "Where are you?" Zera Kodesh (Devarim 'ג במדרש ה"ד) explains that throughout galus, Hashem asks ַיֶּכָּהא, "Where are you?" Hashem searches for us, wondering why we are so distant from Him. He searches until He finds us as it states (Hoshea 9:10) ישראל מצאתי, "I found Yisrael." And when Hashem finds us, He sees that throughout the galus we were also constantly searching for Him. We were always asking, להעריצו כבודו מקום איה, "Where is Hashem so we can exalt Him?"
Hashem and Bnei Yisrael search for each other until they unite. There are times when we merit that unity. On Tisha b'Av, we unite through mourning; on yom tov, we connect through joy.
Mourning and Joy
We cry and mourn bitterly these days, but it doesn't necessarily need to be with sadness.
We quoted above the Chasam Sofer zy'a (Drashos, 7 Av, p.326), who says, "If I weren't afraid, I would say Tisha b'Av is a happy day because we survived..." Hashem poured out His wrath on stones and wood so that we can survive.
Whenever we merit to meet Hashem, it is reason for great joy.
Rebbe Shmelke of Nikolsburg zy'a tells a mashal: A king had to flee from his kingdom. He came to a distant land and stayed at the home of one of his loyal friends. The king noticed that his host was sometimes sad and other times happy. The king asked him, "Are you happy or sad?" The host replied, "I'm both. I'm sad and mournful that you had to leave your palace, and I'm also happy because the king is in my home."
The Gemara (Shabbos 30:) says, שורה השכינה אין שמחה מתוך אלא, "The Shechinah doesn't reside unless there is happiness." A navi needs to be in a state of happiness to receive his prophecy. So, how did Yirmiyahu HaNavi receive the nevuah of Megilas Eichah, since he was certainly crying and mourning as he received this prophecy? The Chazon Ish (Maaseh Ish, vol.4 163, and some say it is from the Brisker Rav zt'l) answers that it must be that one can mourn and cry and be happy at the same time.
Furthermore, mourning results in happiness. Shulchan Aruch (Orach Chaim 554:25) states, בשמחתה ורואה זוכה ירושלים על המתאבל וכל, "Whoever mourns for Yerushalayim merits seeing its joy." The Meforshim (Sfas Emes, Kedushas Levi, and others) explain that ורואה זוכה, "merits and sees," is written in the present tense because due to his mourning, he merits to experience the joy of the redemption even now.
At a chasunah we say the brachah of שוש תשיש, when we daven for the rebuilding of Yerushalayim. The Sfas Emes zt'l explains that due to the Churban, the joy of the chasunah isn't complete. We complete the joy of the chasunah when we mourn for Yerushalayim. The mourning draws down to us a scent of the joy of rebuilding Yerushalayim, and now the joy of the chasunah is complete.
Daven for Mashiach
Rebbe Pinchas of Koritz zt'l (Imrei Pinchas 380-381) writes, "On Tisha b'Av, when we sit on the floor and daven, we can accomplish with tefillah everything we need. If someone lacks something, a good time for tefillah is on Tisha b'Av, when we sit on the earth."
Reb Elyah Lopian zt'l said that in Kelm, they emphasized the word כל in the phrase ירושלים על המתאבל כל בשמחתה ורואה זוכה, "Whoever mourns for Yerushalayim merits seeing its joy..." כל, everyone, even those who committed severe aveiros and don’t deserve to witness the joy of Yerushalayim when it is rebuilt. Nevertheless, mourning sanctifies and purifies; because they mourned, they will merit to see its joy (Beis Kelm, p.396).
