The mitzvah of shmurah matza TB Pesakhim 40

We have to remember that wheat kernels are not hametz. The fermentation process of hametz only begins when water and flour are combined. Today as soon water is introduced to the flour, the baker only has 18 minutes to knead the dough, roll it, pierce it with a fork so the matza will bake through and through, and remove the finished matza from the oven. Any matza that takes longer than 18 minutes is no longer kosher for Passover. Interesting though, today’s Gemara presents us with a much more lenient position. The fermentation process only takes place when the wheat and the water are combined, but are inactive. Any type of activity inhibits the fermentation process. Rabbi Yosei gives an example of this type of activity. “It was taught in a baraita that Rabbi Yosei, son of Rabbi Yehuda, says: In the case of flour into which water is dripping, even if the water drips the entire day the flour will not come to a state of leavening, as the ceaseless dripping prevents fermentation. Rav Pappa said: And that is the case only if one drop drips into the other, i.e., the dripping is continuous, preventing the mixture from settling.” (TB Pesakhim 39b, Sefaria.org translation)

Much of today’s daf TB Pesakhim 40 deals with the issue of soaking (לְתִיתָה) the grain facilitating the removal of the bran in order to produce refined flour. In the course of the discussion Rava introduces the mitzvah of shmurah mitzva. He holds that this soaking is obligatory in order to fulfill a matza mitzvah. “Rava reconsidered and then said: It is not only permitted to soak the grains; it is actually a mitzva to soak them, as it is stated: “And you shall guard the matzot” (Exodus 12:17). The Gemara explains this statement: If it is not the case that grain requires soaking, for what purpose is guarding necessary? If you claim that this verse is referring to guarding when kneading, that cannot be the case, as guarding grain while kneading is not considered guarding. If one failed to protect the wheat from becoming leavened up to that point, it is of no use to be careful while kneading it. Consequently, this mitzva to guard the dough cannot be referring to the kneading stage.”  (Sefaria.org translation)

Rav Huna adds the mitzvah of the eating of an olive size portion shmurah matza to the afikomen. “As Rav Huna said: In the case of dough (meaning matza-gg) prepared by gentiles, if one knows that it has not become leavened, a person may fill his stomach with them on Passover night, provided that he eats an olive-bulk of matza in the end, to fulfill the obligation to eat matza.” (Sefaria.org translation)

Rava insisted the guarding process begins even before the kneading of the dough. It begins when the grain is first harvested in the field. “Rava did not retract his statement that guarding grain must begin before kneading. For he would say to those who cut and tied the stalks [kifei] of grain in the field: When you cut the grain, cut it for the purpose of the mitzva. Apparently, Rava maintains that it is necessary to guard the grain from the outset, i.e., from the beginning of its preparation until its end.” (Sefaria.org translation 

Most authorities are of the opinion that the flour from which the matza is prepared should be specially supervised from the time that the wheat is milled שמורה משעת התחינה. However, some authorities require that the flour be specially supervised from the time that the wheat is cut שמורה משעת הקצירה. To differentiate between them, the name matza refers to the matza which was made from the flour from the time of the milling, while shmurah matza refers to the matza made from the flour supervised from the time of the cutting.

Even though the Gemara seems to permit and Rava makes it obligatory to soak the grain (לְתִיתָה), the Goanim forbade it lest the dough rises and becomes hametz inadvertently. (Shulkhan Arukh, Orekh Hayyim, 453:5)