The Mishnayot on our daf discuss cases where an agent who was sent to deliver a geṭ became ill and could not fulfill his mission. When the geṭ was sent in Israel, the Mishna teaches that the messenger can pass on the responsibility to another; if it was sent from the Diaspora to Israel – a situation where the messenger is obligated to testify that the get had been written and signed in his presence – then the messenger would need to appear before a beit din, which would appoint a messenger to replace the first one.
The Gemara emphasizes that the messenger can only turn over his responsibilities to another if he becomes unable to fulfill them himself, i.e. he becomes sick or suffers some other ones – something beyond his control. According to Rabbi Abbahu, if necessary the second messenger can appoint a third, and the third can appoint a fourth – as many as are necessary to deliver the geṭ.
In response to Rabbi Abbahu’s ruling, Rav Ashi teaches that if the first messenger dies, the power of all of later messengers to carry out the mission is lost, and the geṭ cannot be delivered. Upon hearing his father quoted, Mar bar Rav Ashi said, “Ha d’Aba, d’katnuta he – this statement of my father is from the time he was small.” (Rashi understands this to mean that he said it at a young age, and the ruling should not be relied upon, while the Arukh understands it to mean that he said it in a “small minded” way; i.e. incorrectly), and, in fact, that as long as the original sender – in our case, the husband – was still alive and still wanted the geṭ delivered, the final messenger should fulfill his obligation to deliver it.
Apparently Rav Ashi’s original approach viewed the creation of a messenger as handing over all rights with regard to this issue to him, thus with his demise the mission cannot be fulfilled. Mar bar Rav Ashi points out that in giṭṭin the power of divorce always remains in the hands of the husband.