The Avodas Yisrael zt'l (Shabbos HaGadol, writes, "חמץ symbolizes the yetzer hara. We destroy the chametz (the yetzer hara) on erev Pesach, so we can receive the great holiness that is revealed on the night of Pesach…”
Chidushei HaRim zt’l taught that when Pesach arrives, everyone is clean from sins. Before Pesach, everyone is cleaning, searching, and burning the chametz, which represents cleansing ourselves from sins. Furthermore, the process of cleansing ourselves from all past sins will certainly protect us not to commit any new sins.
Pesach is approaching and we hope to receive the many blessings that this yom tov offers. But we must first clean the utensil — our heart, mind, and body — so we can receive the holiness of the yom tov. If the "utensil" isn't clean, the final product won't turn out right.
When we burn the chametz, it’s a very special time. Chametz represents the yetzer hara, sins, and all other impurities. Therefore, when the chametz is burning, the world is being cleansed from these impurities.
The Ateres Yehoshua of Djikev zt'l would say the famous prayer of Rebbe Elimelech of Lizensk zt'l (printed in many siddurim before Shacharis) when he burned the chametz. At this time, the world is pure, and it is an ideal time for tefillah.
Tzaddikim taught that the war of Gog and Magog, which heralds the coming of Moshiach, will occur on erev Pesach within the three hours when people are burning their chametz. Therefore, in the Hoshanos (Succos) we say, "save us three hours.” We can explain that we are praying to be saved from the war of Gog and Magog, which will transpire during the three hours of biur chametz on erev Pesach.
On erev Pesach, when Rebbe Aharon Chernobyler was about to burn his chametz, he remarked, "Some people think we annul gezeiros with money, but that’s a mistake. Now, when we’re burning the chametz, we can annul all cruel decrees."
Matzah represents taking our life in our hands, to do what we want to - which is to do Hashem’s will. If necessary, we are ready to wage a war against the yetzer hara, to defy his requests, and to do our truest desire, which is abide fully to Hashem’s will.
The world says (in jest): Why do people bury the dead? It's because the dead don’t protest. If we will not protest, and let the yetzer hara do whatever it wants with us, he will bury us alive. We must protest, take control of our life, and battle with the yetzer hara.
One of the ways to fight against the yetzer hara is to be involved in many good deeds. The Rebbe of Kotzk zt’l told his chassidim that their sins don’t bother him as much as that they had time for sins. A person should be so busy with good deeds, that there is no time for aveiros. A person that’s busy learning Torah, davening, giving tzedakah, doing chessed, working as well (with the intention to support his family) doesn’t have time to sin.
The Zohar calls matzah "food of cure," and "food of emunah." By eating the matzah one acquires emunah, health, and many other spiritual and material blessings. All of this is because of the specialness of matzah, which signifies constantly serving Hashem, and battling the yetzer hara.
Tzaddikim said, "One should be involved in avodas Hashem constantly. If you don’t have strength to concentrate on Torah right now, you can still say Tehillim. And if you don’t have strength for Tehillim either, you should give tzedakah…" but always be active and do something in Hashem's service.
Chazal say that wealth and wisdom, and several other things are a matter of mazal, dependent on the mazal each person was born with. What should a person do if he was born with a mazal to be poor or foolish? Must he remain that way his entire life? The sefarim tell that when one says אחד by Shema, he can change his mazal. When Rebbe Yehoshua of Belz heard that the four sons of the Haggadah also imply to the אחד of Shema, he understood that on this night, one has the potential to change his mazal. Even if he was born with a negative mazal, it can be improved, as he attains awareness that Hashem is One, and He does everything that He wants in the world.
Chazal say… 'When a sheep injures one limb, its entire body feels it. So too Yisrael, if one of them sins, we all feel it…'
The rule is, it is proper that the korban Pesach be one because it shows that Hashem is One. The reason the Jewish nation has this mitzvah is because Hashem is One and therefore He chose the Jewish nation, who is one..."