Reference for Gittin 148:1

והתניא מהיום ולאחר מיתה גט ואינו גט דברי חכמים רבי אומר כזה גט

, as it has been taught: '[If he says] From to-day and after [my] death, it is a Get and no Get. This is the opinion of the Sages. Rabbi says, One like this is a Get'.<span class="x" onmousemove="('comment',' V. supra 72b. And since they differ on 'from today etc.' we presume that they agree on 'on condition'. V. Tosaf. s.v. ');">¹</span>

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