Gittin, Chapter 7, Mishnah 4. In the previous mishnah we dealt with a man who gives his wife a get and says to her "from today if I die" - that the get should take effect from the day it was handed over, on condition that he dies. Our mishnah now presents the laws that follow from this situation.
"Lo tisyached imo ela bifnei edim" - She may not be secluded with him except in the presence of witnesses:
The mishnah rules that the wife may not be secluded with her husband except in the presence of witnesses, since it is possible that she is already his divorcee. Two reasons are given for this:
The concern that they may come to have relations for the purpose of kiddushin. Even though the get takes effect retroactively from the day it was written, such relations take place after the get has taken effect, and they would therefore constitute a second kiddushin - which would require an additional get.
According to Rashi, the reason is that in general she is treated as an unmarried woman, and it is forbidden to be secluded with her.
Who qualifies as the required witnesses:
Although the mishnah uses the plural, "in the presence of witnesses," the halachah is that even a single witness suffices. The mishnah continues along these lines:
"Afilu eved" - even a Canaanite slave is valid for this purpose.
"Afilu shifchah" - and so too a maidservant.
"Chutz mishifchasah" - her own maidservant does not help, because she is overly familiar with her: the woman is accustomed to her maidservant and is not embarrassed in front of her, and she might even have relations in her presence. Her presence therefore does not serve as a barrier.
"Mah hi b'osan hayamim?" - What is her status during those days?:
The mishnah seeks to clarify the woman's status during those intervening days. According to Rashi, this is not referring to the case of "from today if I die" mentioned in the first part of the mishnah, but to a different case: the husband says, "This is your get, and you shall be divorced by it from now, while I am still in the world, if I die" - meaning from the moment when I am still alive, one moment before my death. In other words, he wants the get to take effect halachically at the moment preceding his death: on the one hand he is still alive and able to divorce, and on the other hand it is only one moment beforehand.
The mishnah therefore asks what her status is during the intervening days, since at any given moment this could occur. On this the Tannaim disagree:
Rabbi Yehudah: "k'eishes ish l'chol devareha" - she is considered a married woman in every respect for that entire period, since the get takes effect only at the literal moment before his death.
Rabbi Yosei: "megureshes v'einah megureshes" - she is of doubtful status, possibly divorced and possibly not, throughout that entire period, because at every single moment there is a doubt that perhaps this is the moment before his death.
And even though it ultimately becomes clear that he did not die at that hour, we do not apply the principle of bereirah here, and the matter is not determined retroactively. Accordingly, if she committed adultery at that time, she would be liable to bring an asham talui and not a chatas, because at that very moment the matter stood in doubt according to Rabbi Yosei.
In summary: In this mishnah we learned that one who gives a get on condition that he dies - his wife may not be secluded with him except in the presence of witnesses, and the halachah is that even one witness suffices, and even a slave or a maidservant, except for her own maidservant, with whom she is overly familiar. We also learned the dispute between Rabbi Yehudah and Rabbi Yosei regarding her status during those days: according to Rabbi Yehudah she is "a married woman in every respect," and according to Rabbi Yosei she is "divorced and not divorced" - a doubt that stands at every single moment.