Gittin, Chapter 6, Mishnah 2. The Gemara explains that this Mishnah deals with a situation in which the government issued a decree against giving gittin to Jews, and because of this they would hand over the get in secret and then tear it up, so that the get was not in the woman's possession. This is the background against which our Mishnah is set.
"HaIshah she'amrah hiskabel li giti":
A woman who says to a messenger under these circumstances "hiskabel li giti" - receive my get for me - appoints him as an agent to receive it. Since he is an agent for receiving, the divorce takes effect the moment he receives the get. But now the messenger returns after carrying out his mission, and the get is not in his hand, since it was torn up. Therefore the Mishnah says that "tzerichah shtei kitei edim" - she requires two sets of witnesses.
The two sets of witnesses:
"Shenayim she'omrim befaneinu amrah" - two witnesses who testify that in their presence the woman appointed the messenger to receive her get.
"U'shnayim she'omrim befaneinu kibel v'kara" - two witnesses who testify that in their presence the messenger received the get and tore it up.
The Mishnah adds that two separate sets are not required: "Afilu hen harishonim v'hen ha'acharonim" - even if the first witnesses and the last witnesses are the very same witnesses. And likewise "echad min harishonim v'echad min ha'acharonim v'echad mitztaref imahen" - one witness from the set of the appointment, one witness from the set of the receiving and tearing, and one additional witness who saw both things and joins with each of them, so that for each and every testimony there are two witnesses.
A betrothed young woman:
The Mishnah moves on to discuss a betrothed na'arah - a girl between the ages of twelve and twelve and a half who has already been betrothed. Who is authorized to receive her get? On the one hand she has already passed the age of mitzvos, and on the other hand she is still partially under her father's authority. The Mishnah says: "Na'arah hame'orasah hi v'aviha mekablin gitah" - both she and her father are authorized to receive the get, since at this stage she is considered to have the legal power of an adult.
Rabbi Yehudah disagrees and says: "Ein shtei yadayim zochos k'echas" - two hands cannot acquire at one and the same time, and it is not possible that both of them, the daughter and the father, should be entitled to receive the get. "Ela aviha mekabel gitah bilvad" - only the father receives the get as a matter of halachah, while the betrothed na'arah cannot receive it. Understandably, if she has no father, because her father died, then as a na'arah she can serve as the recipient of the get herself.
"V'chol she'einah yecholah lishmor es gitah":
Here the Mishnah deals with a minor whose father married her off, who is below the age of mitzvos and too young to guard her get. There are two aspects to this: either she does not know how to look after the get as a document, or she is a child at play who does not know not to come back - if she is sent away and told not to return, she needs to know not to return; and if she does not grasp and understand this, she is too young to actually be divorced.
"V'chol she'einah yecholah lishmor es gitah einah yecholah l'hisgaresh" - whoever is not capable of guarding her get is unable to be divorced.
And some understand that this applies only when she has no father watching over her; but when she does have a father, even at such a young age she is able to be divorced, since her father will see to it that the get is safeguarded, or that she does not return to her husband.
In summary: In this Mishnah we learned about a woman who appoints an agent to receive her get at a time of decree, about the two sets of witnesses that are required - the witnesses to the appointment and the witnesses to the receiving and tearing - and about the ways they may be combined. We also examined the dispute between the Sages and Rabbi Yehudah regarding a betrothed na'arah, and the rule that whoever cannot guard her get cannot be divorced.