Gemara

2a (Mishnah): One who brings a Get within Eretz Yisrael need not say a declaration. If the Get is contested, it will be verified through its signatures.

4b (R. Yitzchak): There was a city in Eretz Yisrael with two districts, each ruled by a different governor. They would not let people travel between the districts, so a declaration was required for a Get sent from one district to the other.

We must say that Rabah agrees that we are concerned for Kiyum. He says that we are also concerned for Lishmah.

5a (Mishnah): If a Shali'ach from Chutz La'aretz cannot say the declaration, if the Get has witnesses, we are Mekayem it through the signatures.

(Rav Yosef): The Shali'ach gave the Get when he was healthy. Before he said Befanai Nichtav u'Befanai Nechtam, he became deaf.

Question: According to Rabah, we should be concerned lest it is not Lishmah!

Answer: The Beraisa is after people in Chutz La'aretz learned the law of Lishmah.

Question: If so, even if the Shali'ach can make the declaration, why must he?

Answer: We decreed that Sheluchim still say it, lest people forget the law again. Chachamim did not decree in unusual cases such as a healthy Shali'ach who became deaf. Even though a woman who was a Shali'ach to bring her own Get is unusual, they decreed, to make a uniform law of Sheluchim.

(Rav Huna): If two Sheluchim bring a Get from abroad, they need not make a declaration. If they would say that they saw the divorce, they would be believed!

Rabah must say that this is after people learned about Lishmah.

6a: Rabah bar Avuha required a declaration for Gitin sent from one row of houses to the row on the other side of a public road. Rav Sheshes required a declaration for Gitin sent from a group of (three or more) houses to another group. Rava required a declaration for Gitin sent within the same group of houses.

Even though Rava holds that the only concern is Kiyum, the people of Mechuza (Rava's city) are very transient, and do not recognize their neighbors' signatures.

(Rav Chanin): A Get was brought, either from Sura to Neharde'a, or vice-versa, and Rav said 'no declaration is required. If you say it, it helps.'

This means that if the husband will contest the Get, he will be ignored.

64a (Rav Huna): If Reuven says that he gave a Get to Levi only to watch it, and Levi says that he told him to give it to Reuven's wife, Reuven is believed. Had he wanted to divorce his wife, he would have given it himself!

(Rav Chisda): Levi is believed. Since Reuven gave the Get to him, he trusted Levi for whatever Levi will say.

Rishonim

Rif and Rosh (1:2): The Sugya is like Rava. One must say a declaration only where there are not witnesses for Kiyum. A Get was brought, either from Sura to Neharde'a, or vice-versa, and Rav said 'no declaration is required. If you say it, it helps, i.e. if the husband will contest the Get, he will be ignored.

Sefer ha'Zechus: The entire Sugya is like Rava. It is difficult for Rabah why two Sheluchim need not make a declaration, and we are lenient about a Shali'ach who became deaf. Rabah must say that this is after people learned about Lishmah, and we do not decree about unusual cases, but sometimes we make the decree uniform. We do not rely on these weak answers.

Hasagos ha'Ra'avad:. The Gemara asked about a Shali'ach who became deaf before saying the declaration. Rabah said that this was after people in Chutz La'aretz learned about Lishmah. We asked why a healthy Shali'ach must say it, and answered that it is lest people forget again. Why was this difficult? Rabah is also concerned for Kiyum! The Yerushalmi says that now that Chaverim are in Chutz la'Aretz, they know about Lishmah. We must say that Yeshivos are prevalent, and witnesses are available like in Eretz Yisrael.

Rambam (Hilchos Gerushin 7:1): If a Shali'ach brought a Get from place to place in Eretz Yisrael, even if he did not see it written and does not recognize the witnesses, just the husband gave it to him and told him to give it to his wife, he gives it in front of two. Even though we do not recognize the witnesses (on the Get), she is divorced and may remarry.

Rambam (2): If her husband comes and says that he never divorced and the Get is forged, we are Mekayem the signatures. If it is not validated and we do not recognize the witnesses, she leaves her new husband and her child is a Mamzer, for she is not divorced. If the Get was lost, she is Safek divorced.

Rambam (7): If a Shali'ach in Eretz Yisrael said the declaration, even though he did not need to, if the husband comes and protests we do not heed him.

Rosh (6): Rabah bar Avuha, Rav Sheshes and Rava required declarations for Gitin sent from one row of houses to another, from a group of houses to another, and within the same group of houses, respectively. This was because the people of Mechuza are very transient, and are not available for Kiyum. R. Tam says that nowadays, everywhere people are transient, so one must say a declaration.

Ran (DH v'Sugyan): This shows that we follow the current practice.

Poskim

Shulchan Aruch (EH 142:1): If a Shali'ach in Eretz Yisrael said the declaration, even though he did not need to, if the husband protests we do not heed him. It seems to me that nowadays even in Eretz Yisrael one must say the declaration.

Ramban (Sof 5a): Nowadays Eretz Yisrael is like Chutz la'Aretz, for it lacks Batei Dinim and witnesses are not available. Even though they did not decree at first, we find that R. Shimon ben Gamliel required between one district and another within one city. Even if Chachamim argue, that is because within one city surely people recognize the signatures. From county to county, whenever witnesses are not common, a declaration is needed. The initial decree was for wherever witnesses are not available for Kiyum.

Rema: Nowadays, one who brings a Get even from house to house in one city must say Befanai Nichtav u'Befanai Nechtam.

Beis Shmuel (1): The Rambam does not require a declaration within one place. Tosfos requires it, for we are transient like people of Mechuza.

Rema: If the husband is in the city, he may not give a Get through a Shali'ach.

Beis Yosef (DH Kasuv b'Orchos): If he is in the city, he is believed to say that he did not give it for divorce. Bnei Mechuza divorce through a Shali'ach even though he is in the city, for they are transient (he is not around to give the Get). R. Tam says that we are all transient (to obligate a declaration), but we do not say so to be lenient.

Rema: Some say that if the Shali'ach has a Harsha'ah (power of attorney) saying who are the witnesses, this is called Mekuyam, and the Shali'ach need not say a declaration. Some disagree. Our custom is to say a declaration even when there is a Harsha'ah. One should not deviate.

Darchei Moshe (2): Our custom is to write in the Harsha'ah who are the witnesses and we are Mekayem it in the Harsha'ah. However, Seder Gitin (86:9) and the Rivash (318) do not consider a Harsha'ah to be Kiyum. We are concerned lest the initial Get was lost or burned, and this one is Mezuyaf.

Gra (13): Only when there are two Sheluchim, we say that they saw the signatures or recognize them.