Who is the Agent?
Everyone is acceptable as an agent to deliver a get except for… and a blind person”
This teaching in the Mishna is qualified by Rav Yosef in the gemara to refer to a get brought from outside of Israel. Since an agent who brings a woman a get from outside of Israel must say that the get was written and signed in front of him specifically for her, as our Sages decreed, a blind person is not qualified since he cannot testify to that which he could not see.
However, earlier in the masechta (6a) the gemara stated that it is sufficient if the agent even only hears the sound of the pen write the get for her. Tosefot there writes that this “hearing” does not qualify a blind person, as we learn in our mishna, but does not explain the reason. One reason offered is that since a blind agent cannot see, he cannot be certain that the get he heard written for her is the same get that he is actually delivering to her, and cannot definitely testify that it was written and signed in front of him for her. (Rabbeinu Asher)
Assumption of Life
Rava said, “That he already died, we are not worried; that he will die, we are worried.”
With these words, Rava resolves an apparent contradiction posed in the gemara between a statement in the mishna and a teaching in a beraita.
The Mishna states that if a kohen travels overseas, his wife may continue to eat terumah since we assume he is alive until known otherwise. A beraita, however, teaches that if a kohen gives his wife a get, stipulating that it will take effect right before he dies, she is forbidden to eat terumah immediately. Why don’t we allow her to eat terumah in this case as well, based on the assumption that he will continue to remain alive right after she eats, just like we assume he continues to be alive in the case in the Mishna in which he travels abroad?
To answer this question, Rava says the above distinction, “That he already died, we are not worried; that he will die, we are worried.” What is the difference?
The distinction that Rava makes is based on the fact that his chezkat chai tells us only what to assume about his present status. Therefore, when her husband is away, we assume he is still alive at the “present” time and she may eat terumah. However, his chezkat chai does not apply to his future status, which is what we are concerned about in the case in which he gave her the conditional get. Since the chazaka does not tell anything about his future status, we cannot assume he will continue to be alive right after she eats the terumah. Therefore, we are worried he will die at any moment, making her a divorcee a moment earlier, and it will turn out that she wrongly ate the terumah at a time when she was no longer married to the kohen.
Gittin 28 a-b