(Mishnah): How does one separate Tamei Chalah on Yom Tov?

(R. Eliezer): He should not designate the Chalah until it is baked.

(Ben Beseira): He (designates the Chalah and then) places it in cold water (to prevent it from becoming Chametz).

(R. Yehoshua): This is not the Chametz upon which one is warned against Bal Yera'eh and Bal Yimatzei. Rather, one may separate it and leave it until the evening and one need not be concerned if it became Chametz.

The Mishnah is referring to when the dough became Tamei after it was rolled (as it was already obligated in Chalah); but if it became Tamei before it was rolled, one should make the dough into small Kav sized pieces (that are not obligated in chalah).

The Mishnah is also referring to when it was kneaded on Yom Tov; but if kneaded before Yom Tov, it follows the Beraisa that states, "One who kneads dough on Yom Tov should separate its Chalah on Yom Tov. If he kneaded it on Erev Yom Tov and forgot to separate its Chalah, the dough may not be moved and certainly its Chalah may not be separated''.

Question: The Beraisa did not say Iras (he added the water to the flour before Yom Tov) but rather Lash (he kneaded it); however if he would have merely added the water to the flour, it was not yet obligated in Chalah and he would be permitted to separate Chalah on Yom Tov. (This contradicts the Mishnah in the 3rd Perek of Maseches Chalah that states that as soon as the water is added to the flour, Chalah may be separated)?!

Answer (R. Shmuel): It refers to Tamei chalah, that one only separates chalah at the end.

(R. Yosa bar R. Bun): Strictly speaking, for tahor dough, Chalah should be separated at the end; they made an enactment to separate its Chalah at the beginning, lest the dough become Tamei.

The Beraisa refers to the Yom Tov of Pesach, but on Shavu'os and Succos it is permitted to move the dough (as one could separate the Chalah and leave it aside).

(R. Yosa/ R. Chuna): It is even prohibited to move on Shavu'os and Succos, as the Pasuk states (Shemos 12,16), "...no Melachah shall be done on them'' - and separating Chalah looks like an act of fixing.

Question: How is it different from Kenivas Yerek (separating the leaves from the stalks of a vegetable) of Terumah (which is permitted even though one is "fixing'' the vegetable)?

Answer: This (vegetable) is suitable for eating but this (Chalah) is not.

Question (Rabanan of Keisarin): How is this (separating Chalah) different from selecting legumes on Yom Tov (which is permitted as it is needed for eating)?

Question: According to R. Eliezer (of the Mishnah), how should one separate Chalah on Yom Tov?

Answer: He should say in pretense, "I wish to eat this and I wish to eat this'' and then bake all of it. When he has removed it from the oven, he should say in pretense, "I wish to leave this one (but not to eat it) and I wish to leave this one'', and he should then leave one in the oven as Chalah.