[Avodah] Yeast isn't chameitz

[Michael Makovi]

Oats: The Gemara says the five grains are all types of wheat or
barley. However, oats are not a type of either.

(Now, to be honest, the mishna in Kilayim says breeding dogs and
wolves together is kilayim, but this is of course strange, given that
the two are clearly the same type of animal. Perhaps halakha isn't
scientific here; perhaps oats are halakhically a type of wheat/barley,
even though biologically they are not, and conversely, perhaps dogs
are not a type of wolf, even though biologically they most certainly
are. Tzarich iyun.)

Moreover, oats lack gluten, the very ingredient which causes
leavening. Now, I've already said halakha doesn't care about yeast, so
presumably, it doesn't care about gluten either, but this certainly
ought to raise suspicions.

I asked Rabbi Yehuda Herzl Henkin about this. He added, moreover, that
oats were not in the Middle East at the time of the Gemara. Hhe said
that a certain rabbi (whose name I forget) applies a double-stricture,
considering oats to be the five grains as far as being hametz, but not
considering oats to be of the grains for making matzah. I.e., oats can
become hametz, but they cannot be made into matzah. (This rabbi whose
name I forget, didn't want to be so audacious as to eat stam oats on
Pesah, considering them  totally exempt from hametz. But he could of
course be strict, and forbid one to make matzah with oats for the
seder obligation. This is reasonable, I think.)

Of course, it is only Rashi who says oats are one of the five grains;
Rambam rather says two-row barley instead.

Michael Makovi