Shiur Supplement #17 Daf 9b-10a
A. Shenei tziburin [lines 39-43] The gemara discusses the following scenario: There are two piles, one of MATZA and one of CHAMETZ, in front of two houses, one which HAS been checked for chametz and one which HAS NOT. Two mice come and take from the piles, one from the pile of matza and one from the pile of chametz, and run inside, one into the pre-checked house and one into the house that had not been previously checked. However, we do not know which mouse ran into which house.
It is clear that one MUST do bedika in the house that had NOT been checked previously. This would have to have been done even had the scenario with the mice NOT occurred. The question arises, though, with regard to the house that HAD been previously checked: Can we assume that the mouse who ran inside was carrying MATZA or must we concern ourselves with the possibility that it brought CHAMETZ inside, thus necessitating another bedika?
B. Heinu shetei kupot [lines 45-49] Background: The Torah requires one to separate part of his produce to give to a kohein. [Mide'oraita, he can separate even a miniscule amount. However the Rabbis mandate that one should give between 1/40th and 1/60th depending on one's generosity.] This portion is called TERUMA and may be eaten only a kohein and his household. Furthermore, one who is tamei (impure) may not eat it and it is likewise forbidden to make the teruma tamei. None of these restrictions apply to the remaining produce which is called CHULIN. If teruma and chulin become mixed together (and the proportion of teruma to chulin is greater than 1:100) the entire mixture must be treated with the same stringencies that apply to teruma.
The gemara attempts to answer the dilemma involving the mice by comparing our scenario to a similar mishna involving teruma: There are two baskets, one containing teruma and the other containing chulin, in front of which are two measures, one of teruma and one of chulin. One measure falls into the basket of teruma and one into the basket of chulin but we do not know if the measure of teruma fell into the basket containing teruma or into the basket containing chulin. According to the mishna, we can assume that the measure of teruma fell into the basket containing teruma, and the measure of chulin fell into the basket containing chulin. Thus, there is no mixture of teruma in the basket of chulin. [The basis for such an assumption is beyond the scope of this shiur.]
Applying this assumption in the case of the mice, we can say that the mouse holding the CHAMETZ ran into the house that had NOT yet been checked while the mouse who snatched the MATZA ran into the house that HAD been checked. Thus, bedika is necessitated only for the house that had NOT been checked.
C. Tzibur echad shel chametz [lines 3-6] The gemara now discusses the following scenario: There is ONE pile of chametz in front of TWO houses that HAVE both been checked. A mouse snatches the chametz and runs into ONE of the houses. However we are not sure which one.
The question arises whether any of the houses need be checked for chametz again.
D. Heinu shenei shevilin [lines 6-16] Background: A person who comes into contact with something that is tamei [eg. By touching it, lifting it, walking over it - depending on the type of tum'a] becomes tamei himself. In turn, he can defile food by coming into contact with it. If the food was teruma or parts of the sacrifices it can no longer be eaten and must be burned.
The gemara attempts to solve the above-mentioned dilemma [See C] by comparing it to the following case: There are two paths, one which it is impossible to pass through without coming into contact with tum'a (and thus becoming tamei), and one which is free from all tum'a. However, we do not know which is which. Person A walks along the first path and, thereafter, comes into contact with tahor (non-tamei) food. Person B walks along the second path and, thereafter, comes into contact with tahor food.
If ONE person would walk along ONE path only he would be considered tahor, regardless of which path he took. If ONE person would walk along BOTH paths he would definitely be tamei. Thus he would defile any tahor food he came into contact with. However, when TWO people walk along BOTH paths (one on each) another factor comes into play: According to R. Yehuda, if the two come to Beit Din (court) SEPARATELY to ascertain their status, each one is considered to be tahor (as we judge each case separately - as if ONE person walked along ONE of two paths). If, however, they come to Beit Din TOGETHER, BOTH are considered TAMEI. Although only one of them is definitely tamei - it is impossible for us to decide who.
According to R. Yose, though, this distinction is irrelevant. Whether they came to Beit Din separately or together, BOTH are considered to be tamei - we are certain that one of them is tamei, but it impossible to decide who.
Rava (and some say R. Yochanan) delineates the scope of the argument as follows: If the two people come to Beit Din TOGETHER, R. Yehuda and R. Yose agree that they are both TAMEI. If they come to Beit Din SEPARATELY, all agree that they are both TAHOR. If, however ONE came to Beit to ascertain his own status AS WELL as that of the second - R. Yose compares it to a scenario where both came TOGETHER and maintains that they are both TAMEI. R. Yehuda, compares it to a scenario where they came SEPARATELY and maintains that both are TAHOR.
Thus, in the case with the mouse which ran into one house, the outcome would be dependent on when the owners of the houses came to Beit Din to find out the halakha: If they came SEPARATELY, NEITHER would have to do bedikat chametz again. If they came TOGETHER, BOTH would have to do bedika. If ONE came to ask for the two of them - according to R. Yose they would BOTH have to check; according to R. Yehuda, NEITHER would have to do bedika again.
E. Safek al safek lo al [lines 16-17] The gemara now discusses the following scenario: A mouse was seen snatching chametz OUTSIDE a house that had already been checked. However, it is not certain whether or not it actually entered the house [See Rashi s.v. Safek...]. Can we assume that the mouse did NOT enter the house and thus, there is NO necessity to do bedika again, or must we concern ourselves with the possibility that mouse brought chametz into the house and, thus, bedika must be done again?
F. Heinu bik'a [lines 17-24] Background: In deciding cases of doubt (safek) whether someone/ something is tamei or tahor one must take into account the TYPE of PLACE where the safek occured. If the safek occured in a reshut ha-RABIM (PUBLIC domain) one rules leniently and pronounces a judgement of TAHOR. If, however, the safek occured in a reshut ha-YACHID (PRIVATE domain) one rules stringently and pronounces a judgement of TAMEI.
In order to solve the above-mentioned dilemma with the mouse, the gemara cites a dispute concerning the following case: There is tum'a in a field which is part of a bik'a (plain constituting of many fields). A person entered the bik'a in the winter (when it is considered a PRIVATE domain) but is uncertain whether he entered that specific field or not. According to the Rabbis he is considered to be tamei as we are dealing with a safek tum'a in a reshut ha-YACHID. According to R. Eleazar, however, he is TAHOR as we are presented with two doubts: Perhaps he never entered the field in the first place, and even if he did, perhaps he did not come into contact with the tum'a.
In our case, since the obligation to check for chametz is only rabbinic in origin, both the Rabbis and R. Eleazar would agree that it is NOT necessary to do bedika again [See Rashi s.v. ve-chakhamim metam'in].