The Torah tells us in Parshas Acharei Mos that the Kohen Gadol was not permitted to enter the Kodesh HaKodoshim except when bringing the ketores, the incense offering. Chaza”l teach us that if the Kohen was missing even one of the spices that belong in the incense, it was invalid and the Kohen was liable for the the death penalty. The Rem”a mentions that this is the reason why Nusach Askenaz does not say the ketores offering after Shachris. We are afraid that if one is in a rush and says the ketores quickly, he may skip over a word and inadvertently make him self liable for death.
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Rabbi Aharon Dovid Singer
Rosh Kollel, NMB Kollel