The source for this prohibition would appear to be the Gemara at the end of Kesuvos which compares those who leave Eretz Yisrael to idolators. There is apparently, however, a difference between non-Kohanim and Kohanim leaving the country, since Chazal established a special Tum'ah on the entire Chutz la'Aretz and the Kohen is intentionally defiling himself by leaving. Thus, even for Mitzvos and for livelihood a Kohen apparently would not be allowed to leave, as is apparent in Yerushalmi Moed Katan 3:1, and only for marriage or to study Torah at a higher level would he be permitted to leave; see Avodah Zarah 13a.

The second caveat is that once the need to be outside Eretz Yisrael ends, he must return there.

Regarding non-Kohanim, they would be allowed to leave for livelihood, marriage, or Torah study but not to dwell abroad; they must come back as soon as possible. It would seem that this is part of the Mitzvah of Yishuv Eretz Yisrael, a Mitzvah which requires those who live there to maintain their presence there and not leave for good to another place.

Regarding what is included in the borders, the Tzitz Eliezer (3:23) discusses the status of Eilat and concludes that since it was conquered by a king (Shlomo) and in accordance with the Navi, it is like Olei Mitzrayim and the Mitzvah exists there as well. In Ever ha'Yarden, the Poskim (in particular, the Tashbetz 3:198-200) consider it part of Eretz Yisrael for performing Mitzvos and for Yishuv Eretz Yisrael, but it does not have the sanctity of Eretz Yisrael and the Shechinah is not present there.

As for Syria, it would appear that Chazal were ambivalent about living there. In some sources they said that one who buys a house there is like in Jerusalem (Gitin 8). In others (Yerushalmi Shevi'is 6:2) they warned against dwelling there permanently. It would seem that since Syria is Kibush Yachid (was conquered before the rest of Eretz Yisrael and without authorization of a Navi), Chazal consider it part of the land for maintaining property and Jewish presence there but discouraged living there at the expense of living in Eretz Yisrael proper.

Yoel Domb

Your question regarding the Gemara in Kesuvos is valid, since we do not usually derive rulings from Agadic sources. However, there are many other Halachic Gemaras supporting this. For example, the Gemara in Bava Basra (91a) says that unless the economic situation is dire "one does not leave the land of Israel," either because one is depriving oneself of the Mitzvos dependant on the land of Israel (Rashbam) or because one is slighting the land of Israel and harming those who are there. Moreover, there is another Gemara in Moed Katan (14a) which is explained by the Rosh and Ra'avad to refer to a person leaving the land of Israel, and the Gemara clearly prohibits it if not for specific reasons. The Gemara in Kidushin (31b) brings this question of whether one may leave and states that it is forbidden unless one intends to honor a parent, etc.

Thus, the Gemara in Kesuvos is not the only source for this prohibition.

Regarding a Tiyul abroad, the Poskim discuss this point (see, for example, Shevet ha'Levi 5:173), and they distinguish between going for leisure (which would not be allowed) and going for a specific purpose (e.g. for health, or to see the works of Hash-m), which would be permitted if a person intends to return immediately. There is a dispute regarding whether going to graves of Tzadikim warrants leaving the land of Israel (the Sedei Chemed permits, while Rav Kook forbids it).

Regarding going to Eilat, the Tzitz Eliezer bases his view on the Rambam and others who determine Yishuv Eretz Yisrael based on the Olei Mitzrayim. In this respect, the Ritva and Tosfos are a minority opinion. However, the Or l'Tziyon (Rav Ben-Tziyon Aba Shaul, 3:23, notes) maintains that it is Chutz la'Aretz. Rav Sternbuch shlit'a (Teshuvos v'Hanhagos 3:332) seems to concur that it would not be permitted to go there without reason.

Regarding the Golan Heights, that area was conquered by Olei Bavel, and therefore would seem to be within the land of Israel, although there is some discussion in the Poskim about that as well.

Yoel Domb

1) The basis for this interpretation in the Rambam (beginning of Hilchos Terumos) which is explained in the Teshuvah of the Tzitz Eliezer (10:1) in which he proves that even though the Kedushah of Olei Mitzrayim was canceled, when the Jewish nation reconquers parts of Eretz Yisrael they revert back to their Kedushah. He also proves this point from the Tur in Hilchos Eretz Yisrael and from the Mabit.

The Kaftor va'Ferach (ch. 10) maintains that the Kedushah for Yishuv Eretz Yisrael exists in all parts of Eretz Yisrael, even though the Mitzvos of Eretz Yisrael do not apply there since it was not reconquered in the time of Olei Bavel. According to him, the Kedushah is eternal and is not dependent on the Kibush.

However, the Maharit and other Acharonim based on the Tosfos you quoted maintain that the Mitzvah of Yishuv applies only where the Mitzvos apply, meaning where Olei Bavel conquered. This is the rationale of the Rashbam and also may be the reasoning of the Tashbetz (3:200).

2) The Rambam does not count Yishuv, but this does not mean he does not hold it in our time. The commentary Megilas Esther on the Rambam tries to make this claim (in Sefer ha'Mitzvos, Hasagos ha'Ramban 4), but the Avnei Nezer (454) and Pe'as ha'Shulchan (Beis Yisrael 1:14) disprove all of his proofs and state unequivocally that the Rambam holds of Mitzvas Yishuv Eretz Yisrael, although the Avnei Nezer sees it as mid'Oraisa and the Pe'as ha'Shulchan sees it as mid'Rabanan at the present time.

3) A possible source for this is the Gemara in Bava Basra 91a, as well as the Midrashim in Rus, regarding Elimelech. The Gemara says that one should not leave even if food is very expensive, as Elimelech was punished for leaving Eretz Yisrael. The Rashbam says that he is leaving the Mitzvos but the implication regarding Elimelech is that this was not due to Mitzvos but due to the fact that he was harming the land, and this is the Midrash's expression about Elimelech that "he disheartened the people in Yisrael."

The Chochmas Adam (Mishpat ha'Aretz 11:14) writes that there are few Jews in Eretz Yisrael, and their prayers for the Diaspora are more accepted and they are therefore needed in the land and should not leave. (This reason might not apply today.)

But the main reasoning is the Ramban who says the Mitzvah is to not leave the land for foreigners to develop. Every Jew who leaves means that there are less Jews in the country and the Nochrim who are here will develop, buy, and control part of the land, and this is a Bitul of Yishuv Eretz Yisrael.

4. The commentaries on the Torah discuss the status of the Golan Heights, which was known in previous times as the Land of the Refa'im which was ruled by Og, the king of the Bashan. This region was conquered by Moshe Rabeinu and given to the tribe of Menasheh whose members helped in conquering the region. It is also part of the land of the seven nations which makes up the land of Israel, since the Chivi (one of the seven nations) lived there (Rashbam, Bava Basra 56a). The Rashbam rules, therefore, that it is obligated in Ma'aser and is part of the land which must be occupied by the Jewish nation.

The Or ha'Chayim (Bamidbar 32:7, Devarim 3:13) disagrees and maintains that the Land of the Refa'im was not part of Eretz Yisrael because it was not originally intended to be part of it. He bases himself on Rebbi Yosi's expression regarding Ever ha'Yarden that it is not holy like Eretz Yisrael because it was not "given" but was taken by the tribes who wanted to live there. He therefore maintains that such lands are not to be settled but have a certain sanctity because they were conquered by Moshe Rabeinu.

However, the Yerushalmi (Bikurim 1:8) clearly states that the status of the Golan is different from the rest of the eastern Jordan because it was not "taken" by the tribes but "given" by Moshe to the tribe of Menasheh, and therefore it has the same sanctity as the rest of Eretz Yisrael even according to Rebbi Yosi. The Brisker Rav (in his commentary on the Torah) also maintains that the area of the Golan was designated to be given to the tribes and Moshe gave it to Menasheh but it is part of Eretz Yisrael.

From the Yerushalmi in Shevi'is (6:1) we can also derive that the Olei Bavel conquered parts of the eastern Jordan as many of the places mentioned there are east of the Jordan, so that the sanctity remains in these areas.

5. I do not know of a discussion about whether one may go to Syria in modern times, but there is significant discussion about living there in general. As I previously stated, there seems to be some ambivalence regarding living in Syria, since it is Kibush Yachid. However, going there could be considered going to Chutz la'Aretz for a person living in the land of Israel, as it was not conquered by Olei Bavel (although they may have conquered the Syrian side of the Golan Heights). Thus, in Gittin 76a we find the Rabanan from Eretz Yisrael leaving their friends in Akko because they wanted to go abroad and they did not want to leave the land. However, Chazal did want to encourage people (possibly from abroad) to buy there and therefore even permitted buying on Shabbos and writing the documents via a Nochri. Rashi explains that this is for Yishuv Eretz Yisrael, "to banish the Nochrim and to establish Jews there." The Ma'aseh Roke'ach (a commentary on the Rambam) says that this includes Aleppo ("Chaleb") and the surrounding regions; it would be permitted to buy property on Shabbos there.

Yoel Domb

1) The Ma'aseh Roke'ach is in Shabbos 6:11.

2) The Isur to leave Eretz Yisrael is mid'Rabanan. This is evident from all of the Kulos that Chazal made in different circumstances which they could not have done if it were Min ha'Torah.

3a) The Tashbetz (3:288) maintains that the only Heter to leave Eretz Yisrael is for the reasons stated in the Gemara (learning Torah, marriage, and Kibud Av va'Em). The Tur (Orach Chayim 248)quotes Rabeinu Tam regarding a different issue, who says that visiting friends or business is considered a Mitzvah and should therefore be permitted. The Magen Avraham (OC 531:7) derives from this that one may go for other reasons except for a pleasure trip, and therefore Tosfos is actually the source of the Mishnah Berurah's leniency you mentioned. The Mishpat Kohen also understood this to be the view of Tosfos, that he allows going abroad for other reasons. The Maharit (Chidushim on Kesuvos) understood differently, that even Tosfos would not allow going abroad for other reasons.

Additionally, Rabeinu Chaim ha'Kohen (Kesuvos 110b) maintains that the Mitzvah of Yishuv Eretz Yisrael does not apply nowadays. However, the Kneses ha'Gedolah (Even ha'Ezer 75:28) says that even according to this opinion one would not be allowed to leave if he already lived there.

3b) Some Poskim maintain, like the Rambam, that the only Heterim are Torah, marriage, saving money from Nochrim, and Parnasah (Pe'as ha'Shulchan). However, the Shevet ha'Levi (5:173 understands that the Rambam would allow all other purposes besides leisure if a person intends to return to Eretz Yisrael afterwards, and even a pleasure trip intended to see G-d's amazing creations could be permitted.

3c) The rationale here is that saving money or Parnasah is a legitimate reason to leave Eretz Yisrael, as these are part of a person's livelihood which is more important than other Mitzvos. Regarding other Mitzvos, a Kohen should not enter the Tum'ah of Chutz la'Aretz, but a Yisrael could be lenient (except according to the Maharit).

4) You mentioned the Gemara in Kidushin which implies a Heter to leave the Eretz Yisrael for Kibud Av. The Sugya there discusses Rav Asi's request to leave and see his mother, and Rebbi Yochanan tells him, "I don't know." The implication is that there are two equal Mitzvos here, and therefore there is no clearcut decision about which is more important. When Rav Asi went, Rebbi Yochanan gave him a Berachah, but then he found out that his mother was no longer alive and said that had he known he would not have gone. This may imply that Rav Asi regretted having left Eretz Yisrael despite Rebbi Yochanan's Berachah. The Rambam omits this Heter since it is unclear from the Gemara whether Rebbi Yochanan approved or simply blessed Rav Asi as he embarked on his journey.

Some commentators explain that this Sugya is no proof, since Rav Asi was a Kohen and the rules regarding Kohanim are more stringent, but the Rambam apparently did not make a distinction on this issue.

I had another idea about this story. The Gemara previously relates that Rebbi Yochanan had lost his mother and father at his birth. Thus, he had never known Kibud Av va'Em and indeed said, "Happy is he who did not see them" (one's parents), since the degree of the obligation is so strong and so difficult to fulfill properly. Thus, when Rav Asi asked about going to see his mother, Rebbi Yochanan said that he did not know, meaning that he never had a mother and thus could not give advice on the obligation of Kibud Av va'Em. Rav Asi then found out that his mother had passed away, perhaps because he had asked Rebbi Yochanan regarding Kibud Em which was a slightly insensitive thing to do, and on some level Rebbi Yochanan was Makpid on him (which would explain why he gave Rav Asi a Berachah).

Yoel Domb