סימן קי סעיף טו
הַמַּצּוֹת שֶׁהֵם לָצֵאת בָּהֶן יְדֵי חוֹבַת אֲכִילַת מַצָּה בִּשְׁנֵי לֵילוֹת הָרִאשׁוֹנִים, נִקְרָאוֹת מַצּוֹת מִצְוָה. וּצְרִיכִין לַעֲשׂוֹתָן לְשֵׁם מִצְוָה, עַל יְדֵי יִשְֹרָאֵל גָּדוֹל בֶּן דַּעַת, שֶׁהוּא בֶּן שְׁלֹש עֶשְׂרֵה שָׁנָה וְיוֹם אֶחָד, וְאִשָּׁה בַּת שְׁתֵּים עֶשְׂרֵה שָׁנָה וְיוֹם אֶחָד. וּבְכָל הָעֲשִׂיּוֹת יֹאמַר הָעוֹשֶׂה, לְשֵׁם מַצַּת מִצְוָה, אֲפִלּוּ בִּשְׁאִיבַת הַמַּיִם. (כָּל הַדִּינִים שֶׁכָּתַבְנוּ בְּעִנְיַן אֲפִיַּת הַמַּצּוֹת, זֶהוּ לְמִנְהָגֵנוּ שֶׁאוֹפִין הַכֹּל לִפְנֵי הַפֶּסַח. אֲבָל בִּמְקוֹם הַדְּחָק שֶׁאוֹפִין גַּם בְּפֶּסַח, יֵשׁ בָּזֶה עוֹד חֻמְרוֹת יְתֵרוֹת עַל מַה שֶּׁכָּתַבְנוּ. וְכֵן הַנּוֹהֲגִין לֶאֱפוֹת מַצּוֹת מִצְוָה בְּעֶרֶב פֶּסַח לְאַחַר חֲצוֹת הַיּוֹם, צְרִיכִין זְהִירוּת יְתֵרָה).
The matzos with which we fulfill the mitzvah of eating matzah on the first two nights of Pesach are referred to as matzos mitzvah,5According to Rambam, all the precautions that must be taken for matzos mitzvah must be taken for all the matzos that are eaten on Pesach. Magid Mishnah maintains that Rambam’s ruling was only said on an initial stringency, and only regarding violations of these precautions disqualifying the matzos. Chayei Adam writes that the Vilna Gaon insisted that all matzos eaten on Pesach be made with these precautions. (see Biyur Halachah 460:1) and they must be prepared for the sake of the mitzvah by an adult, male Jew of intelligence,6There is a dispute among the Poskim regarding grinding the wheat. Some maintain that the grinding, too, must be done by Jews, but the custom today is to be lenient and permit it even when done by a non-Jew, so long as a Jew is present to watch that it does not become chametz. Nevertheless, where possible, the grinding should be done by a Jew and it is considered a praiseworthy deed when done so. (Ibid. 460:1) aged at least thirteen years and one day, or a female aged at least twelve years and one day. At each stage in the preparation the worker says, leshem matzas mitzvah, ["For the sake of the matzah of the mitzvah."] (This should be said) even when drawing the water. (All the foregoing laws regarding the baking of the matzos refer to our custom that all matzos are baked before Pesach. In an emergency, when matzos are baked on Pesach, there are other stringencies in addition to the ones mentioned above. Those who follow the custom of baking matzos mitzvah in the afternoon of erev Pesach must take special precautions).
תנא דבי אליהו כל השונה הלכות בכל יום מובטח לו שהוא בן העולם הבא שנאמר הליכות עולם לו אל תקרי הליכות אלא הלכות (נדה ע"ג.)