Parashas Bo · Shemos 12:17 · TT note 1
Torah Temimah on Shemos 12:17, note 1 (on וּשְׁמַרְתֶּם אֶת הַמַּצּוֹת) points to Pesachim 38b.
Sefaria — Exodus 12:17
Sefaria — Torah Temimah on Exodus 12:17
Sefaria — Pesachim 38b
E-Daf — Pesachim 38b
English: One might think a person fulfills his obligation with challos of todah or wafers of a nazir — Scripture says “and you shall guard the matzos”: matzah that is guarded for the sake of matzah. This excludes that which is not guarded for matzah but for a sacrifice.
Requirement of intentional shimur for the mitzvah of matzah.
One does not fulfill the mitzvah with sacrificial matzah that was not guarded for the mitzvah of matzah.