The Mishna on our daf teaches that, in the case of a man who dies after giving instructions to a messenger to deliver a geṭ to his wife or a shtar shihrur to his slave, the documents cannot be delivered.
The central question at hand is whether the wife’s divorce or the slave’s release takes effect immediately or only when the document reaches their hands. The general rule is that unless the messenger was appointed by the recipient to accept a document on his or her behalf, it will only take effect when it reaches the hand of the intended recipient. An exception would be a case where the document represents something that is to the benefit of the recipient, where the messenger may automatically become the recipient’s representative. A divorce is not perceived by the Mishna as being to the woman’s benefit; whether or not a slave’s release is to his benefit is the subject of some discussion – see the Mishna on daf 11b.
Thus, it is clear that in our case, the divorce does not take effect immediately and it cannot be delivered after the husband has died. Rashi argues that even according to the opinion in the Mishna that releasing the slave benefits him, still the document that releases him will not work if the owner dies before the shtar shihrur is delivered. The Pnei Yehoshua explains this by suggesting that the language used by the owner indicates that he does not want the release to take effect until the document is actually delivered into the slave’s hands.
Tosafot and most of the rishonim disagree with Rashi, and argue that according to that opinion in the Mishna, once the shtar shihrur is given to the messenger the slave would immediately be freed since the messenger becomes his representative to accept the document. They argue that even if the shtar shihrur is destroyed it makes no difference, since the slave has already been freed. They explain the case of the our Mishna to be true only in a situation where the man commanded that a shtar shihrur be prepared, but that he died before it had been given to the messenger.