To Be For Him for a Nation
In regard to the "Mayim Shelanu" that is drawn before sunset today for the baking of the "Erev pesach" Matzos tomorrow, the Kedushas Levi writes the following beautiful idea. He says that on Rosh Hashana we do "Tashlich", throwing our Aveiros into the sea. Rosh Hashana is Teshuvah Mi'Yirah - repentance out of fear. When a Jew repents out of fear, his sins are erased and "thrown into the sea". However, Pesach is an inyan of "Teshuvah Me'Ahavah - Repentance out of love". When we repent out of love, Chazal say that our previous sins are uplifted to the status of zechuyos - merits. That is why we now draw the water back, since now, the sins that we threw into the water on Rosh Hashana are zechyos! We have uplifted this water, and we can now use it for the holy Mitzva of Matza on the Seder night!
Teshuvah Me'Ahava turns our sins into merits in the same way that light can only be seen from within darkness. When a person reaches a high level of Teshuvah, they recognize that it was precisely their past sins and darkness that enabled / forced them to make the turn-around and come close to Hashem. And it was specifically their difficulties and great distance from Hashem, that made their eventual climb-back-up so precious. When a person reaches Teshuvah Me'Ahava, they recognize that their past sins were really to their merit, in that it was only through them that they were able to make the difficult - yet rewarding - journey that brought them to where they are today.
Pesach / Yetziyas Mitzrayim is a time of Teshuvah Me'Ahava for this very reason. It was only through the servitude and darkness of Mitzrayim that the great light of the redemption and salvation was able to shine forth!
While Rosh Hashana recalls Hashem's kingship over the entire world: "Hayom Haras Olam - today the world was created", Pesach signifies Hashem's love to His people on a much more individualistic basis, through the tremendous Hashgacha u'pratis and miracles that He wrought when taking us out of Mitzrayim to be His nation. That is also why Pesach is the time to tell over to our children: ve'higadeta levincha; the 4 sons, etc. We emphasize the father/son relationship, because this is the relationship Hashem expressed to us when taking us out of Mitzrayim - "b'ni bechori Yisrael - my son, my first born, Yisrael"... Our exodus from Egypt was the time where we felt Hashem's love more than any other time in history!
Searching for - and burning the Chametz both represent the Teshuvah that we do out of love. The search for chametz represents the "cheshbon Hanefesh", and the "burning" of the chametz represents the burning of the Yetzer hara / Ego. We do this Teshuvah out of love and recognition that Hashem is our Father - and he desires us to be his nation. As the Pasuk in Yirmiyah 7:21 (the Haftorah of last week's Parsha Tzav) says: "For I did not speak to your fathers and did not command them on the day I took them out of Mitzrayim about the Olah and the sacrifices... For only this did I command them saying, listen to my voice so that I should be for you a G-d and you shall be for me a nation...