Gemara

(Reish Lakish): If Reuven gave a gift to Levi and Levi said "I do not want it," whoever takes it keeps it.

Question: Why is this different than Rav Sheshes' law?

(Rav Sheshes): If after Levi received from Reuven, he said "it should be Batel," it is Batel;

If he said "I do not want it," his words take effect;

If he said "it is Batul," or "it is not a gift," his words do not take effect.

Suggestion: "His words take effect" in the middle clause mean that it reverts to Reuven.

Answer: No, it means that also Levi does not get it. Whoever takes it keeps it.

(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: Granted, R. Shimon holds that a gift is given on condition that the receiver accept it. If not, it reverts to the giver;

However, if the first Tana holds that saying "I do not want it" makes Hefker, the slaves are (free) Zarim. Why may they eat Terumah?!

Answer: He holds that if one is Mafkir his slave, he goes free and needs a Get Shichrur (of freedom), and that such a slave (even though he need not serve his master, he still belongs to him. If the master is a Kohen, the slave) may eat Terumah.

Gitin 32a: Rabah bar Avuha taught that if one received a gift and then said 'it is Mevutal' or 'Yevutal (it will be Batel)' or 'I do not want it', his words do not take effect. If he said 'it is Batel' or 'it is not a gift', his words take effect!

This shows that 'Batel' implies that it was void from the beginning!

Answer (Abaye): 'Batel' can connote from the beginning, or it should be void. Regarding a gift, he means the former, for that works (to undo the gift).

Bava Kama 116a: Rav Safra was in a caravan. A lion accompanied them. Each night, a member of the caravan would give his donkey to the lion, and the lion ate it. On Rav Safra's night, the lion did not eat the donkey. Rav Safra made an acquisition on the donkey.

(Ravina): Really, he did not need to. He made it Hefker only for the lion, not for others! He did so lest someone contest him.

Rishonim

Rambam (Hilchos Zechiyah 4:1): If Shimon received a gift and acquired it, and after he took it he was quiet, and later said 'I don't want it' or 'I do not accept it', or 'it is Batel', or 'I see this defect in it', Lo Amar Klum (his words have no effect). Just like a giver cannot retract, a recipient cannot retract after he acquired it. Saying 'I do not want it' makes it Hefker. Whoever takes it first acquires it. If he protested from the beginning, he did not acquire, and it returns to the original owner.

Ra'avad: This is only if he said 'Hu Batel.' If he said 'Batel Hu', it is not a gift.

Ran (Gitin 16a DH v'Ha): Why does the Rambam say that 'Hu Batel' takes effect?

Magid Mishneh: The Rambam learns from Bava Basra. The Ra'avad's distinction is astounding. The Gemara distinguishes only between 'it will be Batel' and 'it is Batel.' The texts in Gitin and Kosher are different. Some Meforshim say that it is a Sugya that differs in different places. This is why the Rambam brought only Reish Lakish's law, and did not deal with the different versions of the Sugyos to rule about 'it is Batel.' Surely, it does not return to the owner, since he received it in silence. The Rambam said 'Lo Amar Klum' to teach that it does not return the owner. All Sugyos must agree to this.

Question (Beis Yosef CM 245 DH v'Yesh): This is astounding. The Rambam does not omit laws because there are different texts! He should rule according to the best text! Also, the Rambam said that if he said 'I do not want it', Lo Amar Klum, like the Sugya in Gitin. In Kerisus, we say that his words take effect! Rather, the Rambam taught "Harei Hu Batel', and all the more so 'it will be Batel' or 'Mevutal' (they connote the future, so Lo Amar Klum). The Ra'avad says that if so, we must distinguish this from 'Batel Hu', due to the Sugya in Gitin. The Rambam did not omit anything. We learn 'Batel Hu' from Halachah 12 (that if he says that he never received it, it belongs to the giver).

Kesef Mishneh: What is the Rambam's source to say that if he said 'I saw a defect in it', Lo Amar Klum? This is unreasonable. Perhaps initially he was silent because he thought that there is no defect, and now that he recognized the defect, he protests that he never intended to accept it with a defect! Perhaps the Rambam discusses an overt defect, which surely he recognized from the beginning. Even though he says 'this defect appears to me', which connotes that he saw it only now, since it is overt, we know that he is lying.

Rambam (12): If Reuven says 'I wrote a gift document and gave it to Shimon', and Shimon says ''he did not', a litigant's admission is like 100 witnesses. Reuven eats the Peros.

Rosh (Gitin 4:3): Here, Rabah bar Avuha taught that if one received a gift and then said 'it is Mevuteles', his words do not take effect. Most texts in Kerisus say oppositely! The text here is primary. Rashi said that the text in Kerisus is like the text here, and says that only regarding land, 'I do not want it' has no effect. Regarding Metaltelim, it is Hefker. Since it came to his Reshus, 'I do not want it' means that he removes himself from them. Regarding land, which is not in his hand, it is not an expression of Hefker.

Rosh (Bava Basra 8:51): The Rashbam explains that if he protested from the beginning, he does not acquire Bal Korcho (against his will), but he does not return it to Reuven (the giver), for Reuven withdrew from the property and made it Hefker. Whoever takes it acquires it. This is wrong. If he never wanted to take it, it is not Hefker. It never left Reuven's Reshus! He removed himself from it only on condition that Shimon will accept it, like we say in Bava Kama 116a. Therefore, if he protested from the beginning, it returns to Reuven.

Poskim

Shulchan Aruch (CM 245:10): If Shimon received a gift and acquired it, and after he took it he was quiet, and later said 'I don't want it' or 'I do not accept it', or 'it is Batel', or 'I see this defect in it', Lo Amar Klum to make it return to the owner. Rather, it is Hefker, and whoever takes it first acquires it.

Beis Yosef (DH Mekabel): Rashi explains that if Shimon received a gift and then said 'it is Mevuteles', 'it will be Batel', or 'I do not want it', his words do not take effect. Shimon received it against his will. If Shimon has a creditor, he collects from it, for all of these expressions are in the future. Once he received it, he cannot retract. 'It is Batel' or 'it is not a gift' connote that it was Batel before he received it. He did not acquire it, so it returns to the giver.

Beis Yosef (DH u'Mah she'Chasav): Tosfos and the Ran were bothered by the discrepancies between the Sugyos in Gitin and Kerisus. Rashi says that the Beraisa is not difficult for Reish Lakish. Reish Lakish discusses Metaltelim. Since Metaltelim are in his hand, and he says 'I do not want them', this is an expression of Hefker. Land is not in his hand, so 'I do not want it' is not Hefker. Rather, he does not want the gift to be valid. However, the Seifa is difficult. It says that 'it is Batel' takes effect, for this is past tense, i.e. it was Batel when I took it. His admission is like witnesses (that he never acquired), therefore his words take effect. Alternatively, we could have answered that this is unlike Reish Lakish's law, because here he says that he never received it, so it returns to the owner. One gives a gift on condition that the receiver accept it. If not, it is not a gift. Reish Lakish discusses one who made it Hefker after receiving it for a gift.

Drishah (13): The Shulchan Aruch is like the Beis Yosef's understanding of the Rambam. I say that the Rambam holds that it is Hefker only regarding 'I do not want it', which is like 'Iy Efshi' in the Gemara. He holds that the text in Kerisus is primary, like Tosfos (Gitin 32a DH Mevuteles) says. The Gemara asked against Reish Lakish from the Reisha, in which he said Iy Efshi, and his words take effect. We answered that they take effect to make it Hefker, but not to return it to the owner. The Rambam teaches all the expressions in Kerisus, which do not help at all to return it to the owner, but of them, only 'I do not want it' makes it Hefker. He need not distinguish between land and Metaltelim, like Rashi did.

Gra (14): The Rambam had the text of Tosfos in Gitin. The Sugya in Gitin asked according to the Hava Amina, that his words take effect and it returns to the owner. Abaye answered according to this assumption. The Rambam rules like the conclusion in Kerisus.

Rema: If Shimon has a creditor, he collects from it.

SMA (18): This is when the creditor has a document with witnesses. He has a lien on all Shimon's property, so Shimon cannot make it Hefker and uproot the lien after he acquired it. This applies to expressions that meant that he acquired it, but from now and onwards he does not want it. It is no better than if he sold or gave it to someone else. The creditor takes it from the buyer or recipient. Do not say that the Rema means like the Nimukei Yosef (Bava Basra 63b), that even if it is Hefker, if the creditor took it, this exempts Shimon from his debt, and the creditor cannot say 'I acquired from Hefker. You still owe me.' If so, the Rema would not have written 'the creditor collects from it.'

Shulchan Aruch (ibid.): If he protested from the beginning, he did not acquire, and it returns to the original owner.

Gra (16): This is like Tosfos and the Rosh, and unlike the Rashbam. This is like Kerisus 24b. R. Shimon holds that a gift is given on condition that the receiver accept it. If not, it reverts to the giver. The first Tana agrees (when the receiver does not acquire, e.g.) when he protested from the beginning.

Rema: This is if he says words that connote that he does not want it. If his words connote that it was not a gift from the beginning, even if he was initially silent, we believe his admission. This is even if it harms others, e.g. he has a creditor. Since it was not in his Chazakah until now, he is believed about it. If he said 'I do not want it', if the gift was Metaltelim, it is Hefker. If it was land, since he was initially silent, Lo Amar Klum.

SMA (19): The Rema holds that 'I do not want it' is unlike 'Iy Efshi Bah' that the Mechaber wrote. The Rambam equates them.

Rebuttal (Shach 6): Surely the Rema equates these. He merely cites the Rosh.

Gra (19): The Rema rules like Rashi, the Rosh and Tur (who distinguish land from Metaltelim), unlike the Shulchan Aruch and Rambam.