In a meticulous display of hiddur mitzvah, the Rebbe of Rachmastrivka was seen donning two different shtreimels during the Erev Pesach matzah baking after chatzos hayom on Erev Shabbos.
As the Rebbe entered the matzah bakery to personally participate in the baking of matzos, he wore an older shtreimel for the physical labor of kneading and rolling. Then, the Rebbe stood near the oven and recited Hallel with great dveikus. Before doing so, however, he changed into a different shtreimel.
The reason? Out of an abundance of caution, the Rebbe was concerned that tiny crumbs of flour or dough—potentially turning into chametz—might have remained on the original shtreimel worn during the baking. To avoid any halachic issue during the recitation of Hallel, he switched to a second, clean shtreimel.

{Matzav.com Israel}