Gemara

(Rav Asi citing R. Yochanan): If brothers divided an inheritance (of land), it is as if they sold to each other. In Yovel, they return their portions to each other (due to Ein Breirah. I.e. we cannot say that each brother took the share that was meant for him. Rather, it is as if each traded his proper share for what he took.)

48a (Rav Yosef): Had R. Yochanan not said that Kinyan Peros (owning the yield) is like Kinyan ha'Guf (owing the property itself), his opinion would be ludicrous!

(In Viduy (a Parshah recited when bringing) Bikurim, one thanks Hash-m for "the land that You gave to me.") If Kinyan Peros were unlike Kinyan ha'Guf, one could recite it only if he inherited a field that was never split among heirs, i.e. no one in his paternal ancestry had a brother, from the days of Yehoshua!

Bechoros 52b - Question (R. Hoshaya - Mishnah): The following are not returned in Yovel: Bechorah (the extra portion given to the firstborn)...

Answer (R. Elazar): This means that it is not returned l'Vatalah (for naught).

Question (Rav Sheshes): This implies that the opinion that says that they do return holds that it is l'Vatalah! (This is unreasonable.)

Apparently, Rav Sheshes did not hear Ravin cite R. Yochanan to say that the other opinion holds that they return l'Vatalah.

Bava Basra 136a (R. Yochanan): If one wrote his property to his children for after he dies, and kept the Peros for himself in his lifetime, and the son sold the property and then he died in the father's lifetime, the buyer never gets it.

This is because Kinyan Peros k'Kinyan ha'Guf. The son never truly owned it.

(Reish Lakish): The buyer gets it (after the father dies, for Kinyan Peros Lav k'Kinyan ha'Guf.

(R. Yochanan): If one sold his land for a limited amount of time, the buyer brings Bikurim and recites Viduy;

(Reish Lakish) The buyer brings Bikurim but does not recite.

R. Yochanan needed to teach here that the sale is void. One might have thought that normally, Kinyan Peros k'Kinyan ha'Guf, but a father concedes full ownership to the son, and the sale stands. R. Yochanan teaches that this is not so.

Reish Lakish needed to teach here that the buyer gets it, lest one think that he agrees that Kinyan Peros k'Kinyan ha'Guf when one retains the Peros, for one always favors himself (and keeps full ownership), and the son's sale is void.

Rishonim

Rambam (Hilchos Shemitah v'Yovel 11:20): Brothers that divided an inheritance are like buyers. They return their portions to each other in Yovel, but the division is not Batel. Similarly, a Bechor or a brother who did Yibum returns the extra portion he received and gets a portion corresponding to it.

Ri Korkus and Kesef Mishneh: 'The division is not Batel' means that they do not make a division with new shares. They merely swap the shares. Rashi says that he does not lose it entirely. Rather, he gets back a different portion. This is difficult. How could the Gemara even think that he loses it entirely?! The words of the Gemara 'they return to each other' supports the Rambam.

Question (Tosfos 48a DH Iy Lav): We rule like Reish Lakish, that Kinyan Peros Lav k'Kinyan ha'Guf, and that Ein Breirah for mid'Oraisa laws; brothers who divide an inheritance are like buyers. We said that these are contradictory!

Answer #1 (Tosfos): Reish Lakish and R. Yochanan needed to argue about Kinyan Peros in two cases. We rule like Reish Lakish regarding one who sells to his son (for one pardons to his son), but not in general.

Answer #2 (Tosfos): Only R. Yochanan requires brothers who split an inheritance to return their portions to each other. Other Amora'im hold that even though they are like buyers, only a real sale is returned, but not an inheritance or gift.

Question: The Rambam rules that brothers re-divide in Yovel, and that Kinyan Peros Lav k'Kinyan ha'Guf (Hilchos Bechoros 4:6), even for Bikurim!

Answer #1 (Lechem Mishneh Hilchos Zechiyah 12:13): Reish Lakish holds that normally Kinyan Peros Lav k'Kinyan ha'Guf. However, when one keeps Kinyan Peros for himself, he keeps also Kinyan ha'Guf. Likewise, when brothers divide, each 'sells' to the other Kinyan Peros, and also gives Kinyan ha'Guf, to enable each other to recite Viduy Bikurim. The Rambam was forced to say so because Rava holds that brothers are like buyers, yet he rules like Reish Lakish that Kinyan Peros Lav k'Kinyan ha'Guf.

Answer #2 (Birkas ha'Zevach Erchin 26b Chidushim): Perhaps the Rambam means that if brothers divided in Yovel itself, they need not return their shares. (In such cases, heirs recite.) However, if so, what would be difficult for R. Yochanan?! Also, we hold like Shmuel, that a sale in Yovel is void!

Answer #3 (to both questions - Chasam Sofer 48a DH beha'Hi): The Rambam (Hilchos Mechirah 23:6) says that one who bought land for Peros may not change the land. He may only eat the Peros. One who bought the land for a set time may build and destroy as he wants. The Yerushalmi forbids this to one who buys land when Yovel applies, for it says "v"Shav l'Achuzaso" - the land must be like it was. Normal monetary laws would allow making changes. This Mitzvah of returning land in Yovel forbids. Reish Lakish agrees that when there is no Yovel, one who bought land for 50 years may dig in it. He has Kinyan ha'Guf, and recites Viduy Bikurim. Therefore, a brother who inherited, even though he is like a buyer, may dig in his property. His ancestor who received it in the days of Yehoshua could dig, so this is "v"Shav l'Achuzaso." He has Kinyan ha'Guf. If not, one could not dig a well unless no one in his paternal ancestry had a brother!

Yam Shel Shlomo (Bava Kama Perek 5 Dinei Breirah p.47b): The Kesef Mishneh (Gerushin 3:4) says that we are in doubt whether or not Yesh Breirah, and we are stringent about mid'Oraisa laws. This is wrong. If it was a Safek, we would not force brothers to return their portions and divide again, for perhaps each brother inherited the proper portion!

Answer #4 (Beis Shmuel EH 131:4 and Pnei Yehoshua 48a DH Iy): The Rambam obligates brothers to return in Yovel to fulfill a Safek Mitzvah mid'Oraisa (perhaps Ein Breirah), like the Rashba (25a DH Rav) says.

Pnei Yehoshua: We follow Chazakah, so each brother gets back his portion. Therefore, he is confident (that he will get back his land), and recites. This answers also Tosfos' question.

Rebuttal (Hagahos Baruch Ta'am): It seems that the Rambam holds that they swap portions, like the Ri Korkus and Kesef Mishneh explain.

Answer #5 (Pnei Yehoshua, ibid.): The Rambam (Hilchos Bikurim 4:7) rules that one who bought land recites Viduy in the first Yovel, before the seller is confident. Usually, one is in the first Yovel after he inherited his father.

Rebuttal (Hagahos Baruch Ta'am): After the first Yovel for Klal Yisrael, everyone was confident and no buyer would recite!