Apr 24, 1998 - 19:44 -
I have a question:
Challah is the name of a biblical tithe -- divinely mandated taxes in kind. Whenever one bakes more than a certain amount of dough, a specific share of it must be donated to a kohen (priest).
We no longer know for sure who is a priest (a descendent of Aharon, Moses' older brother). Although family traditions testify to lineage, this is sufficient evidence for ritual honors only -- It is not sufficient evidence for Jewish courts in monetary matters. Therefore, we no longer donate challah to a priest.
However, to ensure that we do not forget about this biblical mitzvah, we follow the rabbinic commandment to burn a token amount of dough. There is a benediction recited before removing a pinch of the dough and tossing it to the back of the oven. And the festive bread enjoyed on the Sabbath is called challah rather than lechem (bread) to remind us to perform this mitzvah.