Gemara

(Chizkiyah): If two witnesses testified that Reuven kidnapped, and two others testified that he sold, and all were Huzmu, they are not killed.

(R. Yochanan): They are killed.

Chizkiyah holds like R. Akiva, who says that testimony must be a (full) Davar (matter), and not a half-Davar. R. Yochanan holds like Chachamim, who say that testimony can even be a Chetzi Davar.

Chizkiyah admits that if witnesses who testified about the second time a Ben Sorer u'Moreh stole and ate (for which he is killed) were Huzmu, they are killed. Since the testimony about the first theft and eating suffice to lash him, also the latter testimony is considered a (full) Davar.

Objection (Rav Papa): If so, Chizkiyah should admit also about kidnapping! Since the witnesses who testify about the kidnapping suffice to lash him, also the testimony about the sale is a 'Davar'!

(Rav Papa): Rather, all agree that witnesses of the sale are killed. They argue about witnesses of the kidnapping. Chizkiyah holds that kidnapping is is not an Aveirah of Misah. It is independent. R. Yochanan holds that it is the first half of the Aveirah (which ends with the sale), so they are killed.

(Abaye): They argue when two witnesses saw a Ben Sorer u'Moreh steal the second time, and two others saw him eat the second time.

Bava Basra 56a (Mishnah): If three pairs of witnesses testified, each about one year of Chazakah, and all were Huzmu, they jointly pay for the field.

(Beraisa - R. Yochanan ben Nuri): If a different pair of witnesses testified about each of the three years of Chazakah, this is a Chazakah.

Aba Chalifta: I agree, but R. Akiva argues. He expounds "(according to two witnesses will be established a) Davar", not a Chetzi Davar.

Suggestion: Chachamim use 'Davar' to disqualify when one witness saw one hair on the back of a 12 year-old girl, and one saw one hair on her front.

Rejection: That is not Chetzi Davar. It is Chetzi testimony! (Each witness says that she only has one hair, so she is still a minor.) Rather, two witnesses saw one hair on her back, and two others saw one hair on her front.

Rishonim

Rif (Bava Basra 30a): If a pair testified about each year, this is a Chazakah. Why is this unlike two who testify about one hair on her back, and two about one hair on her front? There is no Chazakah without all three pairs! My Rebbeyim could not answer this. I say that each pair of witnesses obligates paying for the Peros of that year, so it is a full matter. However, if in the end there is testimony about three years, he has a Chazakah, so he ate his own Peros and he need not pay. Migo it is testimony for Peros, it is testimony for Chazakah. Two witnesses about one hair do not help for anything by themselves, so it is like nothing. It is like testimony about three years that were not consecutive.

Rambam (Hilchos Edus 4:7): Even though we join testimonies in monetary cases, each witness must testify about the full matter. If one testified about part of the matter, and the second testified about part of it, we do not establish it through their testimony, for it says "Davar", and not Chetzi Davar. If Moshe says that Ploni ate Peros of a field in a particular year, and David says that he ate the next year, and Yosef says that he ate the year after that, we do not join the testimony and say that he ate three years, for each testified about Chetzi Davar. Similarly, if one saw one hair on the right, and one.saw one hair on the left on the same day, we do not join them, for each testified about half the Simanim. Even if two testified about one hair, and two others testified about one hair, each pair testified about Chetzi Davar. This is not testimony. If one witness saw two hairs on the right, and another witness saw two on the left, they join.

Hagahos Ashri (Bava Basra 3:68): The testimonies about the field are not Chetzi Davar, for they saw all that could be seen at the time. In the first year, they cannot see about the second year. Also, testimony about one year does not help for Chazakah, but it obligates to pay for Peros.

Rashi (86b DH u'Shnayim): Chizkiyah holds like R. Akiva, who says that the testimony of the theft is invalid, for it is a half-Davar, for it does not obligate even lashes without the latter testimony. R. Yochanan holds like Chachamim, who accept the testimony.)

Chidushei ha'Ran (86b DH Maskif and DH u'Machlokes): Rav Papa explains that Chizkiyah holds that kidnapping is an independent Chiyuv. R. Yochanan holds that it is the beginning of the Chiyuv Misah, so there are no lashes for it itself, so testimony about just kidnapping is Chetzi Davar. Abaye teaches that they argue similarly about Ben Sorer u'Moreh. R. Yochanan holds that the latter theft begins the Chiyuv MIsah, so it does not obligate lashes or money, so testimony just about the theft is Chetzi Davar.

Poskim

Shulchan Aruch (CM 30:13): Eeach witness must testify about the full matter. If they testified about Chetzi Davar, this is nothing. If one saw one hair on the right side of a boy, and another saw one hair on the left, this is nothing, for each testified about partial Simanim. Even if two testified about one hair, and two others testified about the other, this is nothing, for each pair testified about Chetzi Davar. However, if one saw two hairs on the right, and another saw two on the left, they join. The same applies to all similar cases.

Beis Yosef (DH Tzarich): The Gemara discussed one hair on her back, and one hair on her front. The Rambam and Tur explain that this refers to hairs on the right and left. The Gemara says that this is Chetzi Davar and half testimony, and similarly when each of three witnesses testifies that Ploni ate Peros in a particular yeart. If a pair testified about each year, the Gemara explicitly says that this is a Chazakah. Why is this unlike two witnesses about one hair on her back, and two about one hair on her front? The Rif says that it is not Chetzi Davar, because testimony about one year obligates paying for Peros. Tosfos says that it is because they saw all that could be seen at the time. I say that when one saw two hairs on the right, and one saw two on the left, it helps for monetary cases, but not for Gitin and Kidushin, which can pertain to capital cases, for which Edus Meuchedes (the witnesses did not see the other) is invalid. The Rambam connotes like this, for when discussing monetary cases he said that they join.

Bedek ha'Bayis: According to what I wrote above (see the coming entry), Gitin and Kidushin are like monetary cases.

Beis Yosef (DH ul'Inyan keshe'Mekablim): Do we accept Edus Meyuchedes for a matter that would pertain to capital cases if we judged capital cases nowadays? The Rif and Rosh (Gitin 35b and 6:4) bring from the Yerushalmi that if one witness saw a divorced couple secluded in the morning, and one saw them secluded in the evening, they do not join (to say that they had Bi'ah for Kidushin). The Ran explains that we join for monetary cases, but not for Gitin and Kidushin, which pertain to capital cases. The Mordechai brings a Yerushalmi (about witnesses who saw grounds to believe that a married woman was Mezanah) that they join. The Bavli (Kesuvos 26b, Gitin 33b) equates money and Isur, even regarding Gitin, since now it is not a capital case. The Yerushalmi that the Rif and Rosh brought is different. There, the man and woman knew that there is only one witness, so they did not intend for Kidushin, rather, for Zenus. For other matters, witnesses join. However, the Yerushalmi equates this to other matters, and it is a Safek. Therefore, we rule like the Bavli connotes, that they join for anything that is not a proper capital case.

Hagahos Drishah (11): Above in this Siman, the Beis Yosef said that Edus Meyuchedes joins for something that pertains to capital cases, but nowadays we do not judge it! I explain that here, when the latter witness says that he saw hairs on the left, unlike the first witness, Beis Din does not accept this for capital cases, and likewise for Gitin and Kidushin. However, when each of two witnesses say that they saw (the same thing, e.g.) a Kidushin, but from different places, we are not so stringent to consider Gitin and Kidushin like capital cases. The same applies to money. The witnesses testify about the same matter. This is unlike hairs. Since they must see hairs in the proper place, and they did not see in the same place, the testimony itself is Meyuchedes.

Shulchan Aruch (EH 142:12): If in front of witnesses a man made a blind person a Shali'ach to give a Get, he gives it in front of those witnesses, and it is Kosher.

Beis Shmuel (21): He gives it in front of those witnesses, so it will not be Chetzi Davar. This is like the Rif. If neither pair of witnesses would help by itself, it is Chetzi Davar. Tosfos holds that since they saw all that could be seen at the time, it is Kosher. When a woman makes a Shali'ach to receive her Get, why is it Kosher according to the Rif? The witnesses of appointment suffice, for we see it in the Shali'ach's hand.

Chasam Sofer (CM 148): The SMA explains only according to Tosfos. He holds that we rule like Tosfos against the Rif. However, in EH 142, the Shulchan Aruch and Rema rule like the Rif! Also the Rambam, Ramban, Ramah and Tur hold like the Rif. One cannot say 'I am sure that the Halachah follows Tosfos', even if he is Muchzak.