As we have learned, in order to transfer property from one person to another, a kinyan must take place. A kinyan is an act that indicates a final decision on the part of the owner to sell and the purchaser to buy.
The Gemara on today’s daf discusses a kinyan that is done by means of a shtar – a contract or legal document. Rav Hamnuna quotes a baraita that teaches that a shtar is valid if it was written on paper or on clay, even if it is not worth a peruta – a small sum of money. Tosafot point out that there is really no need to teach that the shtar does not have to have inherent value, since it is what is written in the document that creates the kinyan; property transfer based on a shtar is not based on ḥalipin – a trade of two things with value. Some rishonim follow the Ramban in saying that we may have thought that in order for a shtar to be a significant document it must have some minimal value.
With regard to a shtar that is written on clay, Tosafot point out that other sources appear to forbid writing a contract on clay, since soft clay can easily be erased and the terms of the contract changed after it is signed. Among the answers that are suggested are
– that this baraita follows the opinion of Rabbi Eliezer who believes that the kinyan takes effect based on the witnesses who see the shtar transferred between the two parties, rather than being based on what is written in it (see Tosafot and the Ritva);
– that this case is one where the clay was hard and the letters were chiseled into it, so the tablet could not be erased (see the Rashba);
– that the prohibition against using clay is only when the shtar was needed to act as proof of the transaction. In the event that it was needed only to create the transaction at the beginning of the process, it did not need to be a permanent record.