Explanation #1 (Rashbam): The case is, Reuven sold to Levi without Acharayus.

Source: It seems that he explained so, for if he sold with Acharayus, the testimony affects Shimon;

Even though there was despair and Shinuy Reshus (it passed to a new owner), Shimon can take it from Levi, since Levi has no loss, for he can return to Reuven [for compensation];

However, regarding land, in which there is not despair and Shinuy Reshus, it returns to him, like the Rashbam explained, for despair does not help for land.

Question (Ri): In the Yerushalmi, it says that despair helps for land. Even though it cannot be stolen, despair helps for it;

Regarding a slave, it connotes in Gitin (39b) that despair helps, even though slaves are equated to land!

The Ri says that also the Sugya of Sikrikon (an extortionist who kills people who do not give their land to him, Gitin 58b) proves so (that despair helps for land).

Answer (Ri): We discuss when he did not despair.

Implied question: We could have distinguished within the case of a cow or Talis between before despair and after despair!

Answer: [The Beraisa] discusses a common case. It is not common to despair from land when a Yisrael stole it. [Even] if he cannot take it from [the robber], because he does not heed Beis Din, he will take it from his son.

Question: An heir cannot testify for him, for it returns to him, like it says in Bava Kama (111b)!

Anything specific, such as a cow or Talis, they must return due to honor of their father.

Answer: We establish this in Bava Kama (94b) when [the father] repented, but did not have time to return it before he died. Here we discuss when he did not repent.

Explanation: The Beraisa discusses specifically without Acharayus. Then, he can testify about a cow or Talis;

Shmuel's teaching [about a field] applies in every case. He taught a Chidush, that even without Acharayus [he cannot testify about it].

Explanation: Even if Rava holds that slaves are like land, he discusses an Apotiki, to teach that this is whether in a document, or verbally.

Implied question: Why don't we consider a sale together with Hekdesh, that it uproots Shibud?

Answer: This is because Hekdesh uproots [Shibud] even if he was Makneh Metaltelim Agav (along with) land, unlike a sale.

Question: I am unsure if [he must write] this only [when he is Meshabed] Metaltelim Agav land, or even to land alone.

Implied question: We could have asked, if so, also a house or field [he could testify about it, if he sold it right after buying it]!

Answer: We [prefer to] ask from the teaching itself.

Remark: Some say that the custom to write in Harsha'ah "and I gave to him four Amos in my Chatzer", even though he has no land, because there is no man who does not have four Amos in Eretz Yisrael, for land (i.e. what he inherited from his ancestors who entered in the days of Yehoshua) cannot be [Halachically] stolen;

Alternatively, there is no man who does not have [rights to] four Amos to bury him;

Rebuttal #1: Here, it connotes that it is possible that he has no land.

Rebuttal #2: Also Kidushin (60b) connotes like this. [If one said] "you are Mekudeshes to me on condition that I have land..." This connotes that it is possible that he has no land!

It is difficult to establish this to discuss a convert, who has no share in Eretz Yisrael.

Rebuttal #3: If so, a person [without land] could not make two documents of Harsha'ah, for in the first, he already was Makneh his four Amos!

Explanation (R. Tam): The reason is because he admits that he has land, and this is detrimental for him, for through the land, he is Makneh to his friend;

Even if there are several witnesses who contradict him, a litigant's admission is like 100 witnesses.

Observation: We are not concerned for looking like Sheker, like we find (below 149a) regarding Isur the convert. An Odisa (Kinyan through admission) came out of Isur's house, and even though Isur lied [it was Makneh].

Question (Rabbeinu Chizkiyahu): In any case, we should be concerned lest he was Makneh to him Metaltelim Agav land, and he admitted that he has land, even though he never had land!

Answer: We are not so concerned lest he lied to admit.

Pesak (Rabbeinu Chizkiyahu): Nowadays, that we normally write "I was Makneh to him four Amos in my Chatzer", if so this is common;

If so, if one sold to him a cow or Talis, he may not testify for him, even though there are witnesses that he never had land.