"Lishmah" Matzos Mitzvah
20. We learn from the pasuk which says, "You shall guard the matzos" that the matzos used at the Seder must be guarded for the sake of matzos mitzvah, even if there is no specific concern that they became chometz, or there is a sfeik sfeika, or some other reason to permit them (מ"ב תנג סקכ"א ).
21. Klal Yisroel have taken upon themselves to only use matzah that was guarded from the time of grinding, or at least kneading (מ"ב סקכ"ה ) for the sake of matzah throughout the entire Pesach. Some only use matzah that was watched from the time of the harvest throughout Pesach (הגר"א הובא בביאה"ל תנג ס"ד ד"ה טוב ), especially in locales where rain in the summer is common (שו"ת מהרש"ג נו אות ב , מעשה רב אות קפו ).
Definition of Lishmah
22. Lishmah in the context of watching matzos does not refer to intent for the sake of a mitzvah (שו"ת עונג יו"ט סי' ב ). We learn from the above pasuk that the matzos must be guarded from becoming chometz with the intent that these matzos will be used for the mitzvah of matzah.
Saying "Lesheim Matzas Mitzvah"
23. One does not need to specify before making each matzah that it is for matzas mitzvah; it suffices to say it once at the beginning of the process (ביאה"ל תס ס"א ד"ה וקטן ). However, if there was an interruption, or if he relocated (א"א בוטשאטש מהדו"ת ס"ב ), he should be machmir and repeat that everything is for matzas mitzvah.
24. There is an old custom to say "Lesheim matzas mitzvah" at the beginning of the process. This covers the entire procedure of guarding, baking, etc. (מרן פוסק ה דור , מועדים וזמנים ח"ג רסא אות ח ).
25. Some say it should be worded in the future tense: "Anything which will be done today involving this matzah will all be for the sake of matzas mitzvah" (ביאה"ל שם ). Others say it should be in the present tense: "Anything I am doing today..." (חזו"א דינים והנהגות פי"ז אות ב ) or "We are doing everything for the sake of matzas mitzvah" (חזו"א , קובץ אגרות ח"א קפ"ה אות ב ).
26. Some point out that the focus of the lishmah intent is on guarding the Matzos from becoming chometz, not on making the matzos. To emphasize this, it is better to say, "Anything I will do today, and the guarding of the matzos from becoming chometz, is for the sake of matzas mitzvah" (מרן פוסק הדור שם ).
