Rif Pesachim 14b {Pesachim 48b continues; 46b}

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14b

{Pesachim 48b continues}
the basket combines them to require challah {be taken off}, and it is one shared reason. And Shmuel already ruled that the halacha is like Rabbi Eliezer, for Rav Yehuda cited Shmuel: the halacha is like Rabbi Eliezer.
Rabbi Chanina said: Even {if the loaves were} pronged and thus not stuck to one another, the basket combines them to impose the requirement of challah.
However, these words are said in terms of Eretz Yisrael, where challah is Biblical, and since it is ritually impure challah, it is not fit for consumption at all, not for an adult nor for a minor -- and since it is forbidden to bake on Yom Tov something which is not ochel nefesh, and it is also forbidden to burn holy items {kodshim} on Yom Tov, we must say that we should not designate it {as challah} until it is baked. For since it is not yet designated as challah, it does not yet become holy, and as he bakes each and every loaf, we say that this one is indeed fit for consumption {for it is not impure consecrated food}. And when we finally separate one of them and call it challah, we permit the rest of them and forbid that challah alone. And we leave it {=that loaf} until after motzaei Yom Tov and burn it.
However, the challah of outside the land {of Israel}, which is only Rabbinic, does not need anything, but rather we designate it {as challah while it is yet dough}, and even ab initio {lechatchila}, and a Kohen who is a minor may eat it, for Shmuel said {in Keritut 67a}: The challah of outside the land {of Israel} is not forbidden except to one whose ritual impurity comes upon him from his own body - by a male, until he is able to have a seminal emission and by a female, until she is menstruant. And if there is no Kohen who is a minor present, we conduct ourselves like Rabbi Eliezer who says that we do not designate it {as challah} until it is baked, and when Yom Tov exits, we burn it.
And so is the halacha.

{Pesachim 46b}
It was stated {by Amoraim}:
One who bakes on Yom Tov for the week-day:
Rav Chisda said: He incurs lashes.
And Rabba said: He does not incur lashes.