Gemara

A case occurred in which someone slaughtered and then intended to be Zorek or to be Maktir to idolatry. Chachamim did not rule to permit or forbid it.

(Rav Shizbi): They did not rule that it was permitted out of respect for R. Shimon ben Gamliel's opinion;

(Beraisa): If Reuven wrote a document giving all his property (which included slaves) to Shimon, and Shimon said 'I do not want the property', if Shimon is a Kohen, the slaves may eat Terumah (they are his slaves);

R. Shimon ben Gamliel says, once he says 'I do not want the property', Reuven's heirs acquire it.

Question: Does the first Tana hold that Shimon acquires the property in spite of his protests?!

Answer (Rabah): If Shimon protested from the beginning, all agree that he does not acquire. If he was quiet, and later protested, all agree that he acquired. They argue when Levi received the document on behalf of Shimon, and Shimon was initially silent and then protested. The first Tana holds that his initial silence shows that he consented to acquire; and he later reconsidered and protested. This has no effect. R. Shimon ben Gamliel holds that his later protest reveals that from the beginning, he did not want to acquire. At first he felt no need to protest, since he did not take the document.

Bava Basra 137b (Rav Yehudah): If Reuven wrote his property to Shimon, and Shimon said 'I do not want it', he acquires it anyway, even if he screams in protest;

(R. Yochanan): He does not acquire it.

(R. Aba bar Mamal): They do not argue. R. Yochanan discusses one who protested from the beginning. Rav Yehudah discusses one who was initially quiet and later protested.

Rishonim

Rif (Bava Basra 63b): R. Aba bar Mamal discusses a Matanas Shechiv me'Ra (a gift of a sick person who fears lest he die), for his words are as if the matter was given. Once the recipient is silent, he acquired. If a healthy person gave, the recipient does not acquire until it comes to his hand.

Rambam (Hilchos Zechiyah 4:3): If Levi acquired from Reuven on behalf of Shimon, and when Shimon heard he was silent and later protested 'I do not accept it', it is a Safek whether his initial silence was consent; and he later protested to retract. Or, he was silent because nothing came to this hand; his later protest reveals that he never wanted to acquire. Therefore; if David acquired for himself, we do not take it from him. Perhaps Shimon acquired it, and when he said 'I do not want it', he made it Hefker. David acquired from Hefker. If Reuven seized it from David, we do not take it from him. Perhaps since Shimon said 'I do not want it', this shows that he never acquired it and it still belongs to Reuven.

Magid Mishneh: The Rambam rules that it is a Safek, because in Chulin, a case occurred in which one slaughtered and then intended to be Zorek or Maktir to idolatry. Chachamim did not forbid due to respect for Rabanan, and they did not permit due to respect for R. Shimon ben Gamliel. If they were undecided, who will decide?! Ba'al ha'Itur says that the Ge'onim said that it is a Safek.

Rambam (9:13): If a Shechiv Mera wrote all his property to Levi, and Levi said 'I do not want it', he did not acquire.

Rambam (14): If Levi was initially quiet and later protested, he acquired. Words of a Shechiv Mera are as if they were written and given. Once he was silent, he cannot retract.

Rosh (Bava Basra 8:51): If Shimon was initially silent and later protested, it does not return to Reuven. Since he was silent, he acquired it. Later, when he said 'I do not want it', he made it Hefker. This refers to a Shechiv Mera. It is as if his words were written and given over. When a healthy person gives a gift, the recipient does not acquire until the document reaches his hands. R. Shimon ben Gamliel and Chachamim argue about when Levi acquired on behalf of Shimon, and Shimon was initially silent and later protested.

Poskim

Shulchan Aruch (CM 245:11): If Levi acquired from Reuven on behalf of Shimon, and when Shimon heard he was silent and later protested 'I do not accept it', it is a Safek whether his initial silence was consent; and he later protested to retract. Or, he was silent because nothing came to this hand; his later protest reveals that he never wanted to acquire. Therefore; if David acquired for himself, we do not take it from him. Perhaps Shimon acquired it, and when he said 'I do not want it', he made it Hefker. David acquired from Hefker. If Reuven seized it from David, we do not take it from him. Perhaps since Shimon said 'I do not want it', this shows that he never acquired it and it still belongs to Reuven.

Beis Yosef (DH u'Mah she'Chasav): The Tur says that the Rosh connotes that Shimon acquired. This is because the Rosh wrote that the Tana'im argue in a case when Levi acquired on behalf of Shimon, and Shimon was silent and later protested, and he did not say like whom we rule. Presumably, the Halachah follows the first Tana. Also the Rif brought both opinions and did not say like whom we rule. Presumably, also he rules like the first Tana. The Rashbam explicitly rules like the first Tana.

SMA (20): The rule that the Halachah always follows R. Shimon ben Gamliel (except for three places) applies only to Mishnayos. In a Beraisa, we assume that the Halachah follows Chachamim. This is why the Rema and Tur say at the end of this Siman that the Rosh holds that he acquired in every case.

Hagahah in Shach (7): The Shach (171:10) says that Tosfos (Bava Metzi'a 69a DH Ela) holds that the Halachah always follows R. Shimon ben Gamliel even in Beraisos.

SMA (21): In other monetary Sefekos, once one seized, the other cannot seize from him, like we say about two who were fighting about a boat (CM 139:1). Here is different, for we know who was the original owner. And also here, if Reuven seized from David, no one can take it from him. Even if David seized it back from Reuven, we do not let him keep it.

Hagahah in Shach (7): The Shach disagrees with the SMA in his Sefer Takfo Kohen.

Gra (20): The Mechaber rules like he holds in the Sugya of a Kohen who seized a Safek Bechor.

Shulchan Aruch (ibid.): Some say that if it was a Matanas Shechiv Mera, since Shimon was silent when he heard, he acquired.

Bedek ha'Bayis: The Rambam did not distinguish between a Matanas Shechiv Mera and a healthy person's gift, like the Rif and Rosh distinguished.

SMA (22): He acquired, and then made it Hefker. The Rambam (4:1) holds that this is even for land; Rashi and the Rosh hold that it is only for Metaltelim.

Rema: I did not see anyone distinguish between a Shechiv Mera and a healthy person. I see no reason to distinguish. Since he acquired through someone else, he acquires from a healthy person like from a Shechiv Mera. Also the Rosh says that he acquired in every case.

SMA (23): The Mechaber cites the opinion of the Rosh, who holds that the Halachah follows the first Tana. We can say that Chachamim's law is only for a Shechiv Mera, for there are two reasons to say that Shimon acquired from him. Firstly, words of a Shechiv Mera are is if they were written and given to the recipient. Secondly, Shimon was initially silent after Levi acquired. If Reuven was healthy, Chachamim could agree to R. Shimon ben Gamliel, that he was initially silent because he saw no need to protest. The Mechaber wrote in the name of 'some say' only what we must say according to Chachamim, i.e. that regarding a Shechiv Mera, he acquired. The Rema was astounded. Perhaps he knew that this is the Mechaber's intent, but he holds that this is difficult, for Chachamim did not mention a Shechiv Mera. Even though R. Shimon ben Gamliel did, surely Chachamim discuss a healthy person.

Shach (7): The Mechaber rules like he wrote in Bedek ha'Bayis. However, he overlooked the Rambam (9:13,14), who wrote exactly like the Rif and Rosh! The only argument is whether the Halachah follows R. Shimon ben Gamliel or the first Tana. The SMA is wrong. See R. Yerucham and Agudas Ezov (who explain the Mechaber's words 'some say that if it was a Matanas Shechiv Mera...' to mean that in this case, the Rif and Rosh do not require that it came to Shimon's hand. He said 'some say' because the Rambam did not distinguish. Bedek ha'Bayis explicitly said that this is the reason. Indeed, he overlooked the Rambam in Perek 9. The Rema, SMA and Bach did not understand this.

Shach (7): The Beis Yosef said the Rif and Rashbam rule like Rabanan. (Note: R. Yerucham says that the Rif rules like the Rambam.) I.e. Shimon acquired in every case. Also Ra'avan and the Maharshal rule like this.

Gra (21): The Rif and Rosh and also the Tur made this distinction (between a Shechiv Mera and a healthy person) in Sa'if 10 (i.e. when Shimon acquired for himself). In this Sa'if (when Levi acquired for Shimon), the Tur wrote that the Rosh holds that he acquired, i.e. Stam. This connotes the Halachah follows the first Tana. The Rashbam and Nimukei Yosef say so. The Mechaber said that also here, some say..., i.e. also here they distinguish a Shechiv Mera from a healthy person. This is wrong. This is why the Rema says 'and so says the Rosh', i.e. he rules like Chachamim.