The Torah (Devarim 16:8) teaches, "For a six-day period you should eat matzos, and on the seventh day, Atzeres LaHashem." Artscroll translates atzeres as "an assembly to Hashem," while Rashi, in his second interpretation, explains it as a day of ingathering. That is, we are to bring together all the concepts and ideas of the holiday. I'd like to suggest that the celebration of shevi'i and acharon shel Pesach is the culmination of the holiday of emunah - complete and total faith in Hashem - granting us the fortitude to carry that faith forward.
At the Pesach Seder we follow the opinion of Rabbi Elazar ben Azariah who holds that the korban Pesach must be eaten by chatzos even though his colleague Rabbi Akiva permits it to be eaten throughout the night of the fifteenth of Nisan. One explanation is that unlike other celebrations - such as a wedding, bris, or pidyon haben - which celebrate an event that has already occurred (the ring placed on the bride's finger, the circumcision performed, etc.), nothing had yet happened by the start of Pesach night. Pharaoh only awoke and called Moshe and Aharon to free the slaves after chatzos, after hearing the cries of his people in response to the tenth plague.
Logically, then, one would expect us to celebrate after chatzos, since nothing redemptive had happened before that point and we were still slaves, but we do something counterintuitive. At the very first Pesach seder, even before chatzos, we celebrated our emunah that Hashem would somehow extricate and redeem us from Egypt. We therefore finish the afikomen before chatzos to relive and internalize the message of the matzah, which is referred to by the Zohar as michlah d'mihemenusa (bread of faith).
Just as food provides nourishment and medicine provides healing, so too the very act of eating matzah is an injection of faith. It not only commemorates the faith of our ancestors who left Egypt without provisions, but it also empowers us to face and overcome personal and communal challenges. It gives us the strength to weather life's storms with emunah, i.e. with faith in Hashem that everything He does is for the good, even when we do not understand it.
This is the lesson taught by Midrash Rabbah on the opening verse of the Shirah ("az yashir...") which we sing daily in Pesukei D'Zimrah and read from the Torah on shevi'i shel Pesach. According to the Seforno, this is why the seventh day of Pesach is a special yom tov - to commemorate the incredible miracle of the splitting of the Red Sea.
The Midrash notes that Moshe began the Shirah with the word "az", the same word he used earlier to complain to Hashem. In Shemos (5:23), Moshe had said, "Umei'az ba'si el Pharaoh - since I came to Pharaoh to speak in Your Name, he made things worse, and You have not saved Your people." It is not coincidental that the same word - az- is used in both contexts. The Midrash explains that Moshe was now thanking Hashem not only for the salvation, but even for the suffering that preceded it. The Torah introduces the shira as follows (15:1), "then Moshe and b"y chose to sing this song to Hashem, and they said - leimor - the following." What does the last word - leimor - mean? Our rabbis answer that it means to teach future generations this most important lesson which is encapsulated by R' Akiva's statement (Berachos 60b), "kol ma d'avid rachmana l'tav avid - all that Hashem does is for the good". At times we might not understand it or realize it, but our Emunah shleima urges us to weather all storms.
The Brisker Rav, in his commentary at the end of Parshas Shemos, explains: if someone falls ill and then recovers, they will surely thank Hashem for their healing, but they might still wish the illness had never happened. Moshe, however, by using the same word "az", teaches that he and the Jewish people thanked Hashem not only for taking them out of Egypt, but also for the servitude itself. For through their suffering, they became the vehicle by which Hashem's greatness was revealed to the world, as the Midrash teaches that all the waters of the world split, proclaiming to all of mankind Hashem's power and omnipotence. The Shirah is not just thanks for drowning the Egyptians; it is thanks for the entire process that preceded it.
Interestingly, the verse immediately preceding the Shirah says, "Vaya'aminu ba'Hashem u'b'Moshe avdo - and they believed in Hashem and in Moshe His servant." In the very next verse, they say, "Zeh Keili - This is my G-d." Rashi, citing the Mechilta, explains that even a maidservant at the sea saw divine revelation clearer than the great Prophet Yechezkel. If so, why does the Torah use the language of belief (vaya'aminu)? Shouldn't it say they knew?
The answer is that their reward came in the merit of their faith. Rabbenu Bachya, in his introduction to Parshas Beshalach, teaches that the sea did not split immediately when the Jews reached its banks. Rather, each person had to walk into the water, step by step, based on their belief, and only then did the sea split. It was because of this faith that we merited redemption. As the Torah teaches (Shemos 4:31), the people believed that Hashem had remembered them, saw their suffering, and bowed in gratitude. Only after this faith was shown does the Torah begin chapter five: "Afterward, Moshe and Aharon came to Pharaoh." It was the emunah of the people that initiated the process of geulah.
Though the Jewish people physically left Egypt on the fifteenth of Nisan, it was on the twenty-first - the seventh day - that their faith enabled the splitting of the sea and the final severance from Egypt.
Just as we are instructed not to eat anything after the afikomen so that the taste of the matzah remains in our mouths, so too must the lessons of the seder remain with us long after the night ends. The atzeres - the concluding gathering of Pesach - emphasizes the importance of emunah. The stronger our faith, the more we merit Hashem's hashgachah pratis.
I would like to conclude with a careful reading of Tehillim (126), which we recite before Birkat HaMazon on Shabbos and Yom Tov. Shabbos is our declaration of faith that Hashem created the world, freed us from Egypt, and will one day redeem us again. The Psalm begins: "Shir ha'ma'alos, b'shuv Hashem es shivas tzion hayinu k'cholmim - when Hashem will return the captivity of Tzion, we will be like dreamers. Az - then - our mouths will be filled with laughter, our tongues with glad song. Az - then - the nations will declare that Hashem has done great things for His people." The Metzudas David explains that at the time of the future redemption, the Jewish people will look back and see all the suffering of exile as if it were but a fleeting dream. The miracles and goodness of the redemption will be so overwhelming that the pain of the past will feel like a distant memory.
In light of the current war in Eretz Yisrael and the challenging global environment, it is easy to feel daunted and disheartened. But the taste of the matzah, the infusion of belief from the Yom Tov of Pesach, especially emphasized in the Haftarah of acharon shel Pesach, can help us conclude the holiday with complete faith and confidence.
Indeed, the best is yet to come.