Bava Batra

As regards the right of heirship! Is it not obvious [that a father is believed]?  — [The statement] was required in respect of the exemption of his wife from levirate marriage. Surely, this also has been taught [elsewhere]:  'A person who declared at the time of his death, 'I have sons', is believed.  [If he declared], 'I have a brother', he is not believed'!  — There, [the law refers to the case] where it was not known [that he had] a brother,  [but] here [it refers] even [to a case] where it is known  that he had a brother. R. Joseph said in the name of Rab Judah in the name of Samuel: Why has it been stated [that if a person said], 'This is my son', he is believed?  — Because a husband who said, 'I divorced my wife', is believed.  'God of Abraham', exclaimed R. Joseph.  'could he  have proved  that which we have learnt from that which we have not learnt?  If, however, that statement was made, it must have been in the following terms;  Rab Judah said in the name of Samuel: Why has it been stated [that if a person said]. 'This is my son', he is believed? — Because it is in his power to divorce her'.  'Now that you have accepted the principle of  Because',  continued  R. Joseph, 'a husband is believed if he stated "I divorced my wife", because it is in his power to divorce her'. When R. Isaac b. Joseph came,  he stated in the name of R. Johanan: A husband who said, 'I divorced my wife', is not believed. R. Shesheth blew upon his hand  [exclaiming]. 'R. Joseph's "because"  has gone'.  [But] it is not [so]!  For, surely, R. Hiyya b. Abin said in the name of R. Johanan: A husband who stated, 'I divorced my wife', is believed!  There is no difficulty: One  [speaks] retrospectively;  the other,  of the future. The question was raised: [Is a husband who] testified retrospectively  believed as regards the future?  Do we divide [his] statement  or do we not divide it?  — R. Mari and R. Zebid [are in dispute on the matter]. One said, 'we do divide', and the other said, 'we do not divide [it]'. Wherein [is this] different from [the law] of Raba? For Raba said: [If a husband testifies,] 'X had intimate intercourse with my wife', he and [one] other [witness] may combine to procure his death;  his death, but not her death!  — In [the case of] two individuals  we [may] divide [a statement]; in [the case of] one individual  [it is possible that we may] not divide.