When instructing Benei Yisrael regarding the laws of the korban Pesach, Moshe admonishes, "You shall observe the matzot" (12:17).
וּשְׁמַרְתֶּם, אֶת-הַמַּצּוֹת, כִּי בְּעֶצֶם הַיּוֹם הַזֶּה, הוֹצֵאתִי אֶת-צִבְאוֹתֵיכֶם מֵאֶרֶץ מִצְרָיִם; וּשְׁמַרְתֶּם אֶת-הַיּוֹם הַזֶּה, לְדֹרֹתֵיכֶם--חֻקַּת עוֹלָם.
The straightforward reading of this pasuk would interpret it as referring to the mitzva of eating matzot. Moshe here emphasizes to the people that they should properly observe this mitzva.
In the Mekhilta, Chazal understand the word "u-shamartem" here as "you shall guard," rather than "you shall observe." This mitzva requires what we call "shimur," an attentive, watchful eye to ensure that the matza to be eaten at the seder does not come in contact with any leavening agents- with any chametz. Only this matza may be used for the fulfillment of the mitzva of eating matza on Leil Pesach.
Yet, Chazal derive yet another, unrelated principle from this verse, as well. When the pasuk says “ushmartem” - "You shall observe [or, 'guard'] the matzot" (12:17). Rabbi Yoshia in the Mekhilta reads the word "matzot" in this verse as "mitzvot," and thus understands the clause this way: Just as the matza eaten at the seder must have been properly guarded from any chance of fermentation ("chimutz") or delay, so must we protect mitzvot from "chimutz” or delay. We do this by performing them at the first opportunity presented, rather than waiting until a later time. Therefore, we should not pass up an opportunity to perform a mitzvah.
This idea is known as "ein ma'avirin al ha-mitzvot," that one may not pass up or delay the opportunity to perform a mitzvah – is a well known concept within Rabbinic law.
The Ketav Sofer, Rav Avraham Shmuel Benyamin Schreiber, maintains that this halakha is our insurance policy for mitzvah observance. It helps ensure that one does not lose the opportunity to perform a mitzva. One may not pass up such an opportunity because she cannot rest assured that this opportunity will remain until later.
Like in Mitzrayim: Chazal say that were Bnei Yisrael to have remained in Egypt even a single moment longer, the potential for redemption would have vanished. As we commemorate through the consumption of matza and ban against leaven, Hashem wasted no time in taking the nation to freedom. If Hashem would have waited even a moment longer, the Egyptian bondage would have continued for eternity.
It is with this same sense of urgency that we must approach every mitzva opportunity that arises. We never know which moments will return and which will not. Just as God could not delay the Exodus, so must we ensure never to "pass over" the opportunity to fulfill mitzvot.
To add to this idea, the Ketav Sofer’s father, The Chatam Sofer, Rav Moshe Schreiber, suggests that this meaning of the term "ushmartem" comes into play in an aspect of the halakha that applies specifically before the time the mitzva's obligation has even arrived. That is, one must eagerly await and anticipate the arrival of the opportunity to perform a mitzva. Rather than dreading the moment at which the given obligation sets in, one should sit in waiting, anxious and excited over the opportunity soon to be presented to him or her. This explanation adds an entirely new dimension to this halakha. This law not only directs us to not delay in our performance of mitzvot, but, requires that we maintain a certain attitude before the time of observance sets in: That of positive anticipation to perform a mitzvah. This was a key ingredient defining our nation in it's formation. As we read Parshat Bo, let us remind ourselves that our people value and appreciate opportunities to grow and advance in our connection to Hashem and each other. From early on in a person's life, these mitzvot are seen as a privilege rather than an unfortunate hardship or ordeal. For each person's active participation helps connect them and form their identity as a member of Am Yisrael. Women and men, girls and boys. As we continue to journey throughout our lives, may we seek out these opportunities, support them in others and demonstrate our desire and willingness to partake in our committment to Hashem. Shabbat Shalom.