Shiur Supplement #12 Daf 7a
A. De-amar R. Giddel amar Rav [lines 3-6] According to the mishna in Kiddushin (2a) the object with which one betrothes a woman must be worth at least one peruta. An object is considered totally worthless if it is forbidden for one to benefit from it. Therefore, one cannot betroth a woman with chametz from noon of the 14th until the end of Pesach as it is forbidden by the Torah to utilize it at all. Since R. Giddel maintains that one cannot betroth a woman with chametz even when it is only prohibited by the Rabbis (i.e., from the beginning of the 6th hour) it is clear that prohibition against deriving benefit from chametz begins already from this time - just as it does during Pesach itself. Just as one cannot nullify his chametz on Pesach itself, so too he cannot do so already from the 6th hour on the 14th.
B. Chitei kurdenaita [line 5] Very hard wheat from the region of Mount Ararat.
C. Rashi s.v. Afilu be-chitei kurdenaita [second half] Rashi raises the famous question: According to strict Torah law (i.e., Mi-de'oraita) chametz is totally permissible before noon of the 14th and, thus, a woman who is betrothed with chametz at this time should be considered married. How is it possible for the Rabbis to decree that the woman is not married and does not even require a divorce from her suitor, should she wish to marry someone else?
Rashi quotes the answer given in Yevamot (90b): The man must give the woman something that belongs to him in order for the betrothal to take place. The Rabbis have the power to relinquish a person's claim to something that belongs to him and render it ownerless, thereby eliminating his ability to betroth a woman with it. Even if the woman accepts the chametz after the 6th hour, it is not considered that the man has given her anything that belongs to him.
Using a similar line of argument, one could answer Rashi's question as follows: After the 6th hour, the Rabbis decreed that any chametz in one's possession should belong to him only vis-a-vis his ability to transgress the command of the Rabbis. However, it is considered ownerless in all other respects. (Compare this to the statement of R. Elazar on daf 6b.)
D. Amar Raba bar R. Huna [lines 17-18] Raba deals with a scenario where one discovers bread/dough that has become mouldy. If "ribta matza" (there is more matza) he can assume that it is permissible. The term "ribta matza" and in fact the entire law of Raba require elucidation and are explained in the following lines of the gemara.
E. Ela de-lo yadinan [lines 20-31] The gemara attempts to interpret the statement of Raba as relating to the following scenario: One discovers dough and is unsure whether it is chametz or matza - if there was more matza than chametz in the vessel (ribta matza) he can assume that it is permissible.
The gemara finds this objectionable. It would make more sense to determine the status of the dough based on the identity of the last known entity to have been in the vessel: If it was last used for matza, we can assume that the dough is permissible. If it was last used for chametz, we can assume that the dough is forbidden. The logic is proved from the following: If one dedicated money to buy a sacrifice, it may not be used for mundane purposes and only once the animal is bought does the money lose its sanctity. Money which is found in Jerusalem during the festive season (when many people buy korbanot) is assumed to be sanctified even though usually most of the money in city is not sanctified. We do not suggest that the money fell BEFORE the festive season and is, thus, NOT sanctified as the streets are swept every day and anything lying there would have been found already. Similarly, we can assume that one clears out his vessels and, thus, whatever was last used determines the status of the dough.