Li-rifuas R' Alexander Yisrael ben Chaya Marta bi-soch shear cholei yisrael
אין אדם יוצא ידי חובתו באכילת מצה שהיא אסורה לו כגון שאכל טבל או מעשר ראשון שלא נטלה תרומתו או שגזלה. זה הכלל כל שמברכין עליו ברכת המזון יוצא בו ידי חובתו וכל שאין מברכין עליו ברכת המזון אין יוצא בו ידי חובתו:
A person cannot fulfill his obligation by eating matzah which is forbidden to him; for example, a person who ate [matzah made from] tevel, [matzah made from] the first tithe from which terumat [ma'aser] had not been separated, or [matzah] that was stolen.
This is the governing principle: All [matzah] upon which the grace after meals is recited may be used to fulfill one's obligation. If the grace after meals may not be recited upon it, it may not be used to fulfill one's obligation. [Rambam Chametz U'matza 6-7].
Commentary:
A person cannot fulfill his obligation by eating matzah which is forbidden to him; for example, a person who ate [matzah made from] tevel -- produce from Eretz Yisrael from which the agricultural requirements — separation of the terumah (a portion given to priests), ma'aser rishon (the first tithe), and ma'aser sheni (the second tithe) — have not been fulfilled.
[matzah made from] the first tithe from which terumat [ma'aser] had not been separated -- After receiving the tithe from the Israelites, the Levites were obligated to separate a second tithe, as commanded in Numbers 18:26.
or [matzah] that was stolen -- The Jerusalem Talmud, Challah 1:9, states:
Matzah that was stolen: one may not recite a blessing upon it. Rav Oshiah states: This is derived from Psalms 10:3: "The greedy's blessing revolts God."
However, one might think this is true only in the beginning; ultimately (i.e., after eating the matzah), he is obligated to pay him money (and thus the matzah itself is no longer the property of the original owner.)
Rabbi Yochanan states: "A mitzvah is not a sin." Rabbi Yossi states: "A sin is not a mitzvah." Rabbi Illa said: "Only when the mitzvot are performed as prescribed are they mitzvot."
The Shulchan Aruch (Orach Chayim 454:4) quotes the Rambam's statements exactly. Nevertheless, Rabbi Akiva Eiger maintains that since the stolen object no longer belongs to the original owners once it has been eaten, one may fulfill the mitzvah of matzah in this manner. All authorities agree that a person who stole grain or flour can fulfill his obligation with matzah made from it.
Rabbenu Manoach maintains that this instance is not dependent on the general rulings governing mitzvot performed with forbidden objects. Rather, Pesachim 38a draws an analogy between the mitzvot of matzah and Challah. Since there is an explicit teaching requiring a person to own the dough he uses for Challah, it thus follows that the matzah he uses must also be his undisputed property.
This is the governing principle: All [matzah] upon which the grace after meals is recited -- even though there are certain halachic difficulties regarding eating it, as explained in Hilchot Berachot 1:20.
may be used to fulfill one's obligation -- to eat matzah on Pesach.
If the grace after meals may not be recited upon it, it may not be used to fulfill one's obligation -- In Hilchot Berachot 1:19, the Rambam states: "Anyone who eats a forbidden food, whether intentionally or unintentionally, does not recite a blessing over it." This includes even foods prohibited by Rabbinic law alone.
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There are many issues with this Rambam. One is that the halacha of not being yotzei with matza of tevel is ONLY according to Rav Shimon who paskens אין איסור חל על איסור [as we see in Pesachim 35b-36a] and the Rambam paskens that איסור חל על איסור which means that one should be yotzei with tevel!!
