Amemar said: The law is [according to Rabbi] that letters are acquired by mesirah. R. Ashi said to Amemar: '[Is this] a tradition or a logical deduction?' He replied unto him: '[It is] a tradition.' R. Ashi said: This may also be deduced logically, because letters are words, and words cannot be acquired by means of [other] words. And [can they] not? Surely Raba b. Isaac said in the name of Rab: There are two [kinds] of deeds. [If a person says], 'take possession of the field on behalf of X, and write for him the deed', he may withdraw the deed but not the field. [If, however, he says, 'take possession of the field] on condition that you write for him the deed', he may withdraw both the deed and the field. But R. Hiyya b. Abin says in the name of R. Huna: There are three kinds of deeds. Two have just been described. [And the] third is one which the seller writes before [the sale],