(Mishnah): One need not be concerned that a weasel dragged Chametz from house to house and from place to place, as otherwise, one would need to be concerned about [dragging] from courtyard to courtyard and from city to city and this [concern] would be endless.

Question (Gemara - Rebbi Yonah): The Mishnah should have first taught from city to city and then from courtyard to courtyard etc. as if one is concerned about dragging from city to city, all the more so one must be concerned about courtyard to courtyard?!

Answer (Rebbi Yosa): The Mishnah is fine - [it should be understood as follows-] if one is not concerned about from house to house, all the more so one need not be concerned about place to place... etc. Is it possible for all Jews to check at the same time?!

(Mishnah - Rebbi Yehudah): One checks on the night of the 14th, in the morning of the 14th and at the time if Biur (destroying the Chametz).

(Chachamim): If he did not check on the night of the 14th, he must check on the [day of the] 14th; and if he did not, he must check during the festival; and if he did not, he must check after the festival.

Whatever he leaves over after checking should be hidden away to avoid the need to check again.

(Gemara - Rebbi Yochanan): Rebbi Yehudah requires checking three times to correspond with the three times that the Torah prohibited Chametz - (Shemos 13,7) "...and Chametz may not be seen in your possession and leaven may not be seen in your possession within all of your borders'' [and the Torah also states (Devarim 16,4) "And leaven will not be seen in your possession within all of your borders''].

Question: What about the pasuk (Shemos 12,15), "You must destroy leaven from your houses''?

Answer: That is a positive mitzvah!

Question: What about the pasuk (Shemos 12,19), "For seven days leaven may not be found in your houses''?

Answer (Rebbi Yosa): Since the phrases [of the first pasuk (Shemos 13,7) and this pasuk (Shemos 12,19)] need each other, they are counted as one pasuk -

"...May not be seen in your possession'' - one might think that if it is deposited with you it is permitted; therefore the pasuk states "...may not be found in your houses''.

''...May not be found in your houses'' - one might think that if he allowed someone to leave Chametz in his home without (the home-owner) taking responsibility for it, it would [still] be prohibited; therefore the pasuk states, "may not be seen in your possession''.

So what do we conclude from this two phrases? If it was deposited with him, it is prohibited; if he allowed it to be left in his home without taking responsibility it is permitted.

Question: The opinion of Rebbi Yehudah has been switched?! -

(Our Mishnah) - (Rebbi Yehudah): One checks on the night of the 14th, in the morning of the 14th and at the time if Biur (destroying the Chametz). The Chachamim say - If he did not check on the night of the 14th, he must check on the [day of the] 14th. (One can deduce that Rebbi Yehudah does not agree that one must check at any later point than the time of Biur, since from the pasukim we learned the obligation to check 3 times only. However, one can assume that the continuation of the Mishnah that states that "...if he did not check during the festival, he must check after the festival'' is agreed to by all (since the Mishnah at that point did not use the word 'im').

This raises a contradiction in Rebbi Yehudah - Surely it is a kal vechomer - if one is required to check 3 times before the the time of Biur, all the more so that one would need to check 3 times after the festival, not just once?!)

Answer: The statement in the Mishnah, that if one did not check during the festival he must check afterwards, is according to the Chachamim (but according to Rebbi Yehudah, in such a case he must check 3 times after the festival).