The Rama writes that we eat egg on leil ha'seder because egg is a symbol of mourning, and we know that whatever night of the week seder night falls out on, 9 Av will be the same night of the week. We find other connections between 9 Av and Pesach -- this relationship is the theme of the kinah which contrasts "
b'tzeisi MiMitzrayim," the greatness of Klal Yisrael and the miracles experienced during the exodus, with "
b'tzeisi m'Yerushalayim," the tragedy of the churban. At the kinos program at Yeshiva Darcehi Torah this morning R' Naftali Jeger, R"Y of Shor Yoshuv, quoted R' Yonasan David as explaining the connection between the two as follows: The gemara (Yevamos 46a) says that when a ger wishes to convert, he/she is told that the Jewish people are now a persecuted, downtrodden, afflicted people -- why would he/she possibly want to join the nation of Klal Yisrael? If the potential ger answers, "I know -- and I am not worthy,
aini k'dai" he/she is immediately accepted. Rashi adds, "
u'mi yitein v'ezkeh l'kach," the ger says, "If only I were worthy of suffering along with them!" At the moment of yetziyas Mitzrayim, the Jewish people collectively underwent geirus by accepting malchus shamayim and the mitzvos of leil haseder. 9 Av is another type of geirus we underwent as a people -- 9 Av is the geirus that comes of participating in Jewish suffering.
Ultimately, with the coming of Moshiach, the tragedies of galus will be revealed as necessary steps on the road to geulah and part of Hashem's chassadim. Hashem is a "
mavi go'el," in the present tense, because all our trials and tribulations are steps down that road. R' Greenberg, a R"M at Yeshiva of Far Rockaway, quoted the Derashos Chasam Sofer on Chanukah that the gematriya of Yisachar = 830, which corresponds to the 410 years of bayis rishon + 420 years of bayis sheni. Chasam Sofer explains that even though the name Yisacher is written with two letter
sins, we pronounce only one because the silent
sin = 300, the number of years we lived under Greek dominion during bayis sheni, when we were not truly a free country. After the future geulah we will look back and see how even those years were filled with chasdei Hashem. After geulah we will pronounce Yisachar as it is written, with a double-
sin. R' Greenberg brilliantly suggested that this is the meaning of Hashem's message of comfort to Rachel Imeinu, "
Yesh sachar l'peulaseich v'shavu m'eretz oyev."
Yesh sachar = the same letters a Yisachar, a foreshadowing and hint to the day when we will be able to pronounce Yisachar properly. (See
here for fantastic another vort said over by R' Greenberg.)
(Any errors in writing these ideas over are mine alone and should not be attributed to the Rosh Yeshiva or R' Greenberg.)
I saw an interesting din quoted by the Chasam Sofer in his derashos. He quotes a Mechilta that after yetziyas Mitzrayim, the year of the date was reckoned from yetziyas Mitzrayim. Had we still had a Beis haMikdash, we would count years since the binyan habayis. However, since we are suffered the churban, the year is counted based on the time elapsed since the churban. The Chasam Sofer goes on to write that he is fulfilling this din and he mentions that the year of his derasha was exactly x number of years since churban habayis. I don't know if your bank will accept a check if you write the year as 1941, the number of years since the churban, but it apparently is something halacha wants us to be aware of. Why? I think the answer is that it's not enough to know there was a mikdash, there was a churban, we are in galus, but more than that -- we we need to be also aware of just how long and painful this galus has been. Nineteen hundred plus years of pain is a long time. Nineteen hundred plus tisha b'Av's spent on the floor reading kinos is a lot of mourning. Ninteen hundred plus years is a long time to keep a memory of a Mikdash alive. Yet, we have done so and continue to do so, and in that zechus will hopefully see the Mikdash again very soon.