Gemara

28a (R. Yochanan): I heard that we learn Chazakah of three years from a Mu'ad ox. An ox that gores three times changes its status from Tam to Mu'ad. Likewise, if one is Machazik (uses a field it) for three years, it changes from the Reshus of the Muchzak (original owner) to the Machazik's Reshus.

(Rava): One is careful with his document only up to three years.

Question (Abaye): If so, a Macha'ah (the Muchzak announces 'he is stealing my land') not in front of the Machazik should be invalid! The Machazik can claim 'had you told me, I would have guarded my document longer!'

Answer (Rava): The ones who heard the Macha'ah surely told their friends, who surely told their friends... (surely, the Machazik found out).

29b: Shimon claimed that he bought Reuven's house, and lived there the years of Chazakah. Reuven denied selling it, and said that he was living in the inner rooms of the house (so Shimon has no Chazakah).

Rav Nachman: Shimon must prove that he was alone in the house.

Objection (Rava): Shimon has a Chazakah. To take the house from him, the burden of proof is on Reuven (to prove that he lived in the inner rooms)!

30a: Moshe claimed that he bought David's house, and lived there for three years. David said 'I did not sell it. I was doing commerce abroad.'

Moshe: I have witnesses that you returned for 30 days every year!

David: All 30 days, I was busy in commerce.

(Rava): It is normal that one is busy in commerce for 30 days.

38a (Mishnah): There are three regions for Chazakah: Yehudah, Ever ha'Yarden and Galil. A Chazakah is valid only if the Muchzak (Levi) was in the same region as the Machazik (Yosef).

R. Yehudah says, it is valid in any case. We require three years for Chazakah is in order that Levi will have time to protest, even if he is overseas!

After Yosef uses the land for one year, people talk about this. Word reaches Levi in one year, and he has another year to come and protest.

Question: If Chachamim validate a Macha'ah not in front of Levi, Chazakah in a different region should be valid! If they disqualify a Macha'ah not in front of Levi, Chazakah in the same region should be valid only in front of Levi!

Answer (R. Aba bar Mamal): Really, they hold that a Macha'ah not in front of the original owner is valid. Our Mishnah discusses a time when there is hostility between the regions. The Tana mentioned Yehudah and Galil to teach that they are considered to have hostility with each other even in peacetime.

(Rava): A Macha'ah not in front of the Machazik is valid.

Rishonim

Rif (15a): The Halachah follows Rav Nachman against Rava. The Machazik must prove that the Muchzak was there.

Rambam (Hilchos To'en 11:2): If the Muchzak says that he he did not protest because he was far away, we say that surely he heard within three years. Therefore, he should have protested in front of witnesses 'Ploni stole from me. Later, I wil take him to Din.' Since he did not protest, he caused his own loss. Therefore, if there was war or the roads between Shimon and Reuven were ruined, even if Reuven ate for 20 years, we take it from him and give it to Shimon, for he can say that he did not know that Reuven was using his land.

Rambam (5): If Shimon protested in a distant land, Reuven cannot claim 'I did not hear that he protested, to be careful with my document longer.' We say 'your friend has a friend, and he has a friend... there is a Chazakah that you found out. Therefore, you should have been careful with your document. If you were not, you caused your own loss.

Rosh (3:6): Some learn from the case with David that if the Muchzak says that he was away for the three years of Chazakah, he is believed, and the Machazik must prove that the Muchzak was here. I say that it is no proof. Perhaps it was known that David was abroad! It seems that the Machazik need not bring a proof. Since he made a Chazakah, word spreads even to other countries. The Muchzak must prove that he was in a place where his protest would not have been heard, and therefore he did not protest.

Drishah (CM 143:2 DH v'Chol): The Rosh says that since there is no proof that the Muchzak is believed, it is more reasonable to say that he is not believed. Even though we discuss whether he heard about the Chazakah, the Rosh says that he must prove that he was in a place where a Macha'ah would not have been heard, for we assume that he surely heard.

SMA (143:5): The Rosh teaches that not only he is not believed to say that he did not hear at all; rather, even if he says that he heard close to the end of three years and there was no time for his protest to be heard, he is not believed.

Ba'al ha'Ma'or (14a): Abaye asked 'if so (a buyer is careful with his document for three years), a Macha'ah not in front of the Machazik should be invalid!' He should have asked that a Chazakah not in front of the Muchzak should be invalid, which is more similar to Shor ha'Mu'ad (it becomes Mu'ad only if witnesses testified about it in front of the owner)! He asked about Macha'ah, for Chazakah depends on (lack of) Macha'ah. If Macha'ah not in front of the Muchzak were invalid, Chazakah not in front of the Muchzak would be invalid.

Rebuttal (Milchamos Hash-m): The Sugya refutes this. One opinion disqualifies Macha'ah not in front of the Muchzak, but Chazakah not in front of the Muchzak is valid! We initially understood that Rava asked that if Macha'ah not in front of the Muchzak is valid, he should be able to protest where he is. Rava agrees that Chazakah not in front of the Muchzak is valid, for the Mishnah lists three regions for Chazakah. If the Machazik and Muchzak were both in Yehudah, the Chazakah is valid even if it was not in front of the Muchzak. He should have come to protest! Also, we suggested (38b) that Rav requires Macha'ah to be in front of the Machazik, even though he holds like R. Yehudah, who allows Chazakah not in front of the Muchzak. I explained how we can distinguish them. How can we answer the Ba'al ha'Ma'or's question? Chazakah not in front of the Muchzak is unlike Shor ha'Mu'ad, for Chazakah is prone to become known. One normally asks about who is on his land. If he despaired and did not ask, it left his Reshus. People do not ask if anyone protested, just like one does not ask if his ox gored. If testimony about goring was not in front of the owner, it does not make a Mu'ad; therefore, he was not careful with his ox. One does not find out about Macha'ah not in front of him, and he is not careful with his document.

Poskim

Shulchan Aruch (CM 143:1): A Chazakah for three years is valid even if the Muchzak was away in a different country, if caravans are frequent between them. If there was war or the roads were ruined, it is not a Chazakah. The Muchzak can say 'I did not know that someone is Machazik in my house.'

Nesivos ha'Mishpat (1): The Mechaber disqualifies a Chazakah not in front of the Muchzak because the Muchzak did not know. The Gemara tried to prove from the Mishnah (38a) that Macha'ah not in front of the Machazik is invalid. Tosfos (38b DH Ein) proved from here that we assume that the Muchzak hears, just his Macha'ah would not be heard. The Rosh and Tur hold that we assume that the Muchzak heard, but he is believed to say that he did not hear.

Shulchan Aruch (2): This is only when we know that the Muchzak was not in the country. If it is not known, we do not heed his claim that he was not here until he clarifies it through witnesses.

Gra (9): This is like Tosfos (29b DH bi'Schunei), who says that it is unreasonable to require the Machazik to bring witnesses who know that the Muchzak was not there even two days of the three years.

Ketzos ha'Choshen (3): We hold like Rav Nachman, who requires the Machazik to clarify his Chazakah. That is when there is a Safek if he made a proper Chazakah. If one made a Chazakah, the Muchzak must prove that he made a Macha'ah. The Chazakah was heard even far away, but if Macha'ah would not have helped, it is as if he made a Macha'ah. The Muchzak must prove that he made, or it is as if he made, a Macha'ah. If we would say that a Chazakah is not heard far away, the Chazakah would be in Safek, and the Machazik would need to bring a proof.

Shulchan Aruch (146:1): A Macha'ah nullifies a Chazakah even if it was not in front of the Machazik, even if he was in a different country, if caravans are frequent between them. It must be in front of witnesses. Two witnesses suffice, even if they are old and sick and cannot inform the Machazik, for they can tell others, who can tell others, until the Machazik will hear.