While the taste of matzah is still in our mouth from the Afikoman (and according to the Gaon of Vilna (Maaseh Rav 185) there is still a mitzvah kiyumis lechatchila to eat matzah each day of Pesach and thereby reify the biblical description of eating matzah for seven days (Shemos 23:15)) I would like to share an insight to the Hagadah that is relevant to all of Pesach and indeed the entire year.
Right before we begin Rav's hagadah of "mitchila ovdei avodah zara hayu avoseinu - originally our ancestors were idol worshipers" (Pesachim 116a) we declare, "yachol meiRosh Chodesh - one might think that the obligation to discuss the exodus commences on the first day of the month of Nissan." What would prompt one to celebrate on Rosh Chodesh? At first glance, as the Torah teaches (Shemos 12:2) it was on Rosh Chodesh Nissan that the Jewish nation experienced a revelation of Hashem to Moshe and Aharon to be communicated to them. This Divine occurrence and relationship is certainly worth celebrating. However, I believe there is much more.
The first mitzvah given to the fledgling nation in Egypt was not only their unique calendar, but the ability and mandate to sanctify. The Medrash (Shemos Rabbah 15:2) teaches that prior to this first mitzvah, any and all kedusha in this world came from Hashem. With the exodus that changed and the Jewish people "shall be holy for Me, for I Hashem am Holy, and I have separated you (the Jewish people) from the peoples to be Mine" (ibid 15:24.) On Pesach we not only celebrate our emergence from slavery to freedom and royalty (Sefer Hachinuch 16), but also from slavery to sanctity. The Medrash continues, "the nation of Israel is holy and they sanctify the month, in addition they sanctify Me".
Sefer Shemos begins with the very formation of the Jewish people, hence it is called the Second Book (see Netizv's introduction to Shemos) the first book deals with the creation of the world and the second deals with the creation of the Jewish nation. We were created with the capacity and the charge to sanctify ourselves and the world about us. Hashem liberated the Jewish people with a mission: we were to accept His Torah fifty days after the exodus and through our living and fulfilling His Torah with which He, The Holy One, is one, we become filled with sanctity.
Moreover, says Rab Chaim Voloziner, (Nefesh Hachaim 1:3) the effect of our actions is way beyond our comprehension. Our positive acts, words, and even holy thoughts generate kedusha in this world and beyond. The Talmud (Berachos 64a) explains the verse "and all your sons will be disciples of Hashem, and abundant will be the peace of your sons" (Isaiah 54:13) to mean, "do not read your sons but your builders." The Nefesh Hachayim takes this most literally. Hence, the observance of Shabbos by Jews in one location might well prevent assimilation and intermarriage in another. This injection of kedusha - sanctity, according to the Ohr Hachaim Hakadosh, is renewed annually, as the verse states, "It is God who takes them out of Egypt" (Bamidbar 23:22) using the word "takes - motzei'um" which includes the present.
Two cases in point: if one was to train a monkey to bake matzah, and we would all watch the monkey move with alacrity in a completely chometz-free environment, and complete the baking within eighteen minutes, that matzah could be eaten on Pesach it is chometz-free but could not be used at the seder to fulfill one's mitzvah of matzah. What is missing is the lishma - the thought and speech of man that endows this unleavened bread with the characteristic of "bread of faith" (Zohar.)
The holiest object of the Jewish people is the sefer Torah. Once again it is not the calligrapher that creates a holy object. It is the sofer - scribe who before he writes a single letter articulates that it is being written for the purpose of the sanctity of the Torah Scroll. His character, persona, and his personally living the Torah endows the sefer Torah with sanctity.
"Yachol merosh chodesh", yes, I would have thought we should celebrate on Rosh Chodesh Nissan, as that is the anniversary of our being endowed with sanctity. On this Shabbos chol haMoed Pesach, which has a double sanctity of both Hashem and man, as He established the sanctity of Shabbos and the Jewish nation the sanctity of the holidays, may we live up to the potential and faith that Hashem has invested in us.