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Shmura Matzah refers to Matzah that is guarded from water beginning from the time of harvest, or at the very least from the time of grinding. Matzos Mitzvah refers to guarding the grain for the sake of the Mitzvah of eating Matzah. The following are the details regarding Shmura Matzah, and the concept of Matzos Mitzvah. Today, all handmade Matzahs have the status of Shmura Matzah and Matzos Mitzvah.
Matzos Mitzvah-Guarding the grains for the sake of Pesach: On the first night of Pesach, one only fulfills the Mitzvah of eating Matzah, with Matzah that had its grains supervised from becoming Chametz for the sake of Pesach, for the sake of Matzos Mitzvah [i.e. Lishma]. [Meaning, that in addition to the fact that all Matzahs eaten over Pesach must be guarded from Chametz, the Matzahs eaten on the night of the 15th/16th must also be guarded Lishma, for the sake of the Mitzvah.] Some Poskim rule it must be guarded for the sake of the Mitzvah to eat Matzah on the night of the 15th of Pesach. However, other Poskim rule that it suffices to guard it for the sake of the Mitzvah of eating Matzah throughout the seven days of Pesach. Practically, the main opinion follows this latter approach. Any Matzah which was not made Lisheim Matzos Mitzvah may not be eaten on the first night of Pesach for the sake of the Mitzvah, even if it was guarded from the time of harvest from becoming Chametz.
Shmura Matzah-Beginning the guarding from the harvest: The grains of all Matzos eaten on Pesach must be supervised from becoming Chametz. From the letter of the law, the grains must only be supervised when the flour is mixed with water. However, the custom of all Jewry is to supervise the wheat used for all the Matzos Mitzvah eaten on the night of the 15th and 16th, from water, beginning from the time that it is ground into flour. Furthermore, it is proper for one to be stringent if possible and supervise the grains beginning from the time of harvest. Practically, the Jewish people are holy and are accustomed to guard the grinding of the grains used for all the Matzahs eaten on Pesach, and not just of the first night. [This form of Matzah is known as Shmura Matzah, as its grains have been guarded from the time of harvest.]
Must a Jew grind the kernels? The grinding of the kernels for Matzos Mitzvah may be done by a gentile, as long as there is a Jew who is supervising him, and thus guarding the grains from becoming Chametz.
The kneading: The kneading, rolling and baking of the Matzos Mitzvah eaten on the first night of Pesach, is disputed amongst the Poskim if it must be performed by an adult Jew for it to carry the status of Lishma, and practically we are initially stringent. The person doing the kneading recites Lesheim Matzos Mitzvah when place the flour into the bowl and when he places the water into the flour.
Should one eat Shmura Matzah on all days of Pesach? The Jewish people are holy and are accustomed to eat Shmura Matzah all the days of Pesach, and not just for Matzos Mitzvah of the first night.
Consumer information for various types of Matzahs on market
Understanding Rasham versus Rashi Matzahs:
Some Matzah bakeries offer two different types of Matzah; one called Rasham and the second called Rashi. The Rashi Matzahs are traditionally more expensive. To the unaware, this may seem like Matzahs which follow two different opinions of Rishonim, however, in truth it does not refer to any person or opinion but rather to the form of grinding. Rashi means “Reichaim Shel Yad” or hand ground Matzah. Some opinions require that the grains be made into flour by a Jew. Rasham means “Reichaim Shel Mechona”, or machine ground flour. Admur rules that there is no need for a Jew to grind the Matzahs, as stated above, and hence, in his opinion, there is no need to purchase the more expensive Matzah called Rashi. Other Poskim concord with this view and negate the stringency of Rashi Matzahs.
 Admur 453:14
 Admur ibid and 460:1; Or Zarua 2:249; Rikanti
The source: This is learned from the verse “Ushmartam Es Hamatzos”, which means that the Matzahs are to be guarded for the sake of the Mitzvah of Matzah. [Admur ibid]
Other opinions: Some Poskim rule that one fulfills the command of eating Matzah on the night of the 15th even if the Matzah was not made Lishma, and as the Mitzvah of Ushmartem Es Hamatzos is an indepednet detail to the Mitzvah. [Oneg Yom Tov 42; Eretz Tzevi, brought in Yechaveh Daas Yechaveh Daas 1:14; 3:26; See Rivash 402; Tashbetz 3:260; Az Nidbaru 11:37; Minchas Yitzchak 8:37; Kinyan Torah 3:56; Lehoros Nasan 4:40; Teshuvos Vehanhagos 2:211]
 M”B 453:21
 See Admur 477:10
 Admur 453:15
 Admur ibid; See Yechaveh Daas 3:26
The reason: The reason for this is because the guarding is only required from a time that the flour is close to becoming chameitz, which is when it comes into contact with water. [Admur ibid]
Other opinions: Some Poskim rule that Matza’s Mitzvah must be guarded from the time of harvest in order to fulfill one’s Mitzvah of eating Matzah. [Peri Chadash 453] We do not rule like this opinion. [Makor Chaim 453; Noda Beyehuda 79; See Yechaveh Daas ibid]
 The reason: The reason for this is because from the time of grinding and onwards, the kernels can become chameitz, as many times there is water used in the grinding process. [Admur ibid]
 The reason: The reason for this is because from the harvest and onwards it is possible for the grain to become chameitz, and there are opinions who say that Rabbinically one only fulfills his obligation with Matzah if the grains was supervised from the time that it can become chameitz, which is from the time that it is harvested. However, prior to harvest there is no need to guard the grains, as so long as the grain is still attached to the ground, it cannot become chameitz. [Admur 453:19] However, if the stalks of grain have become ripe enough to have dried, and thus no longer have a need for the nurture of the ground, then they need to be guarded from water even prior to the harvest. [M”B 453]
 Admur 453:16; Taz 460:1; Chok Yaakov; Chasam Sofer 128; Shaareiy Teshuvah 453:8; The grinding, unlike the kneading, may be done by a gentile, as long as there is a sane Jew who is supervising him, and thus guarding the grains from becoming chameitz.
Other opinions: The Bach rules that this is dependent on the dispute in 460 regarding kneading. Practically, the P”M 460 and Biur Halacha 460 rules that due to this, if possible it is proper to get Matzahs that were ground by hand and not machine. However, clearly according to Admur there is no need for this stringency. These two forms of grinding have found their difference in the names Rasham and Rashi, which mean Reichaim Shel Yad Or Mechona [hand ground or machine ground].
 Admur 460:1
 Bach 453; P”M 460; Biur Halacha 460 “Ein Lashin”; See Piskeiy Teshuvos 450:6; Regarding the custom of the Chabad Rabbeim, and the original custom in Lubavitch-see Otzer Minhagei Chabad 11 that a hand mill was used.
 Admur 453:16; Taz 460:1; Chok Yaakov; Chasam Sofer 128; Shaareiy Teshuvah 453:8
 Beir Moshe 7 Kuntrus Elektri 49; Az Nidbaru 5:34