Rif Pesachim 5a {Pesachim 10b continues ... 13a}

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5a

{Pesachim 10b continues}
he does not need to go back and search again, for we learnt {in the Mishna}, "They need not fear that a mole dragged from the house to house, etc."

And where he searched and afterwards spied a mouse entering the house with a loaf in his mouth, even though he {=the person} subsequently entered the house and found crumbs, we do not say that the mouse ate that loaf and these are its crumbs, but rather we say that these crumbs are from elsewhere and he needs to search for this loaf of the mouse.

For Rava said: A child enters with a loaf in his hand, and he {the adult} enters after him and sees crumbs, he does not need to search, for it is a child's way to make crumbs. A mouse enters with a loaf in its mouth and he enters after it and sees crumbs, he needs to search for it is not a mouse's way to make crumbs.

{Pesachim 11b}
Mishna:
Rabbi Meir says: They may eat the entire five, and must burn it at the beginning of six.
Rabbi Yehuda says: Thay may eat the entire four and they must suspend the entire five, and burn at the beginning of six.

{Pesachim 12b}
Gemara:
What is the reason {according to Rabbi Yehuda} they may not eat the entire five? As a decree for a cloudy day, for since there is no sun visible, he may come to err and confuse the fifth with the seventh {hour}.
If so, even the fourth, he should not eat?!
Rav Papa said: The fourth is everyone's mealtime, and he will not come to err.
Rav Nachman cited Rav: The halacha is like Rabbi Yehuda.

{Pesachim 13a}
The Sages learnt {in a brayta}: The 14th {of Nissan} which fell out on Shabbat, they destroy all {chametz} before Shabbat, and burn teruma {which is chametz} which has suspect, impure, and pure status, and they leave over food for two meals from the pure in order