The Midrash (Shemos Rabba 2:6) says, "Whenever Hashem's presence is revealed, it is forbidden to wear shoes." The kohanim didn't wear shoes in the Beis HaMikdash because Hashem's presence was in the Beis HaMikdash. When Moshe came to the burning bush, Hashem told him to take off his shoes.
The Korban Pesach was eaten while wearing shoes, as it states (12:11) ת ּ ֹאכְ לוּ וְכָכָה ...בְּר ַגְל ֵיכֶם נַעֲל ֵיכֶם ...אֹתוֹ "So shall you eat the [korban Pesach]... your shoes on your feet..." On the night of yetzias Mitzrayim, Hashem's presence was revealed in Mitzrayim, as it states (12:12) מ ִצְר ַיִם בְאֶרֶץ וְעָב ַרְתִּי וּבְכָל בְּהֵמָה וְעַד מֵאָדָם מ ִצְר ַיִם בְּאֶרֶץ בְּכוֹר כָל וְה ִכֵּיתִי ה ַזֶּה בַּלַּיְלָה 'ה אֲנִי שְׁפָט ִים אֶעֱשֶׂה מ ִצְר ַיִם א ֱלֹהֵי , "I shall go through the land of Mitzrayim on this night, and I shall strike every firstborn in the land of Mitzrayim, from man to beast; and against all the gods of Egypt I shall mete out punishment – I am Hashem." The Maharil Diskin asks that since Hashem's presence was in Mitzrayim on that night, shouldn’t they have gone without shoes? Why did they have an obligation to wear shoes specifically?
Maharil Diskin answers that at the time of yetzias Mitzrayim, it was necessary that Bnei Yisrael have bitachon, to trust that Hashem would save them. Their emunah and bitachon brought about the salvation. Therefore, Hashem had them put on shoes, as if they were ready to leave. (They also were girded with a belt, and they held their walking staff in their hands.) They had to demonstrate that they trust Hashem will redeem them from Mitzrayim. This was so important that it overrode the general benefit of not wearing shoes when Hashem's presence is there.
Bnei Yisrael are מאמינים בני מאמינים, believers, the children of believers. Hashem told them to leave Mitzrayim, and they did so, even before they had time to prepare food for the voyage. As it states (12:39) לָהֶם עָשׂוּ לֹא צֵדָה וְגַם, "nor had they made provisions for themselves." Rashi writes, "This is telling the praises of the Jewish people. They didn't say, 'How can we go out to the desert without food?' They had emunah and went. As it states (Yirmiyahu 2:2) כְּלוּלֹת ָ יִ ךְ אַהֲבַת נְעוּר ַ יִ ךְ חֶסֶד לָ ךְ זָכ ַרְתִּי זְרוּעָה לֹא בְּאֶרֶץ בַּמִּדְבָּר אַחֲרַי ל ֶכְת ֵּ ךְ , "I recall for you the kindness of your youth, the love of your youth, your following Me into the Wilderness, into an unsown land." They trusted in Hashem, and this merit is remembered in all generations.
It states (12:34) יֶחְמָץ טֶרֶם בְּצ ֵקוֹ אֶת הָעָם וַיִּשָּׂא שִׁכְמָם עַל בְּשִׂמ ְלֹתָם צְר ֻרֹת מִשְׁא ֲרֹתָם , "The people picked up their dough when it was not yet leavened, their leftovers bound in their garments on their shoulders." Rashi teaches that מִשְׁא ֲרֹתָם means the matzah and maror left over from last night's seder. The Torah tells us that they packed them in their clothes, and placed them עַל שִׁכְמָם , over their shoulders. Why is it important to know exactly how they carried the matzah and maror? Zera Kodesh (Haggadah Shel Pesach, from Rebbe Naftali Ropshitzer zt'l) says that this is another indication that they relied solely on Hashem. A person casts on his shoulder that which he doesn't pay much attention to. This is how the Jewish people left Mitzrayim. They hardly took food along with them, and whatever they did have, they threw over their shoulders. This is all because they trusted Hashem to support them.
Indeed, miraculously, that drop of matzah was all they needed. They ate it for thirty days, and then the manna fell for forty years. They left Mitzrayim with bitachon, and Hashem supplied them with food and with all their other needs.
The reason for yetzias Mitzrayim and the ten makos was to teach emunah, and the parents will teach it to their children. As it states (10:2)...ָבִּנְך וּבֶן ָבִנְך בְּא ָזְנֵי תְּסַפ ֵּר וּלְמַעַן, "So that you may relate in the ears of your son and your son's son..." The following words of the pasuk are 'ה אֲנִי כִּי וִידַעְת ֶּם, "you will know that I am Hashem." The Maharam Shik zt'l (בא ,שיק ם"מהר ליקוטי) asks why it doesn’t say כִּי וְיָדְ עוּ 'ה אֲנִי , "They will know that I am Hashem." If the purpose for the makos is to tell the children the miracles that occurred, the end of the pasuk should use the words אֲנִי כִּי וְיָדְ עוּ 'ה , "they [the children] will know that I am Hashem," not 'ה אֲנִי כִּי וִידַעְת ֶּם, "So that you may know that I am Hashem."
The Maharam Shik quotes an answer from Rebbe Yehoshua of Belz zy'a. If a person desires to teach emunah to his fellow man, he must be accomplished in this matter, himself, because then it will be מן היוצאים דברים הלב אל נכנסים הלב, "Words emanating from the heart that enter another person's heart." But if the person doesn't have emunah, his words won't be influential. The pasuk therefore says, ...ָבִּנְך וּבֶן ָבִנְך בְּא ָזְנֵי תְּסַפ ֵּר וּלְמַעַן, if you want to teach emunah to your children and to your grandchildren, 'ה אֲנִי כִּי וִידַעְת ֶּם, you must first know it yourself. You have to attain this emunah first, and then you can teach it to others.
The same applies to concepts of mussar. You must be interested in the lesson yourself, so you can influence others.
