Q. In Ask the Rabbi question30 you write:
“(It is still prohibited to tread with your feet on the crumbs on the floor, Mishnah Berurah 180, 10)”
But doesn’t the MB (444:15) write that you may walk on the crumbs?
A. On question 30 we wrote: “Horav Shlomo Miller Shlit”a pointed out that in the case of Pesach matzah, the hefetz shel mitzvah would be the matzah that was already eaten but not the remainder. This unused matzah would only be restricted to the normal prohibitions of bizui ochlin, which don’t affect pieces less than a kezais, even on bread. (It is still prohibited to tread with your feet on the crumbs on the floor, Mishnah Berurah 180, 10).
As a hidur mitzvah only (enhancement of the mitzvah) it would be better to collect those pieces and place them inside a plastic bag prior to their placement in the refuse bin or to use them in any other honorable way.”
Indeed Mishna Berura (444: 15) writes regarding Erev Pesach on Shabbos, that ‘pirurin dakin’ or very small bread crumbs can be discarded by just leaving them on the floor. Since people step on them (as they do with floor dust), since they have been already rendered unusable, they change and mix into the debris on the floor and convert into and are part of that dust itself. This is very different than the “pirurin shein bohen kezais” ot don’t have the size of a full olive (about 28 g,), which are likely recognizable and still fit as bread.
We must add, that even regarding the ‘pirurin dakin,’ Mishna Berura (ibid.) adds that it is still better to sweep and wipe the floor using a Gentile or with a shinui, (in an unusual way). Likely, because of the curse of poverty involved, as mentioned in Shulchan Aruch (ibid. See also question 2902).
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit’a