1) SENDING MAIL BEFORE SHABBOS
OPINIONS: The Gemara quotes a Beraisa that teaches that one may not send a letter with a Nochri on Friday that he will deliver on Shabbos, because it appears that the Nochri is doing a Melachah for the Jew. However, if one arranges with the Nochri, before he departs with the letter, to give him a payment for his services, then he may give the Nochri a letter to deliver even though he might deliver it on Shabbos. Alternatively, if there is enough time for the Nochri to reach the house closest to the boundary of the city (according to Beis Hillel) to which the letter is being sent, one may send it with the Nochri on Friday.
The Gemara adds that there is a difference between a city which has a "Bei Davar" and a city which has no "Bei Davar."
What is a "Bei Davar," and why does a "Bei Davar" make a difference whether one may send a letter with a Nochri to that city? Furthermore, why does this unique condition exist only with regard to sending letters, and it was not stated with regard to any of the other acts that a Nochri might do for a Jew on Shabbos (such as delivering utensils to another place)?
(a) RASHI explains that a "Davar" is a person to whom the letter is addressed (literally, it refers to an important person in the city, to whom one usually sends letters). If the addressee is not known to be in the town, then a Jew may not send a letter with a Nochri even if he will reach the house closest to the edge of town before Shabbos. The reason for this is because if the addressee is out of town, then the Nochri never reached the house closest to the edge of the town of the addressee's actual location. If the Nochri continues traveling on Shabbos with the letter in order to deliver it to the addressee, it will look as though he is doing Melachah for the Jew on Shabbos.
What is the difference between sending a letter with a Nochri and sending a pot or utensils with a Nochri (or sending hides to a Nochri for processing)? The Halachah with regard to sending other items is that if one pays the Nochri, then he may send the item before Shabbos. If one does not pay the Nochri, then he may send the item only if there is enough time to reach the destination (or to process the hides) before Shabbos arrives. Only with regard to sending mail is there a separate condition (the "Davar" or addressee must be known to be in the city). What is the reason for this difference?
The answer is that with regard to deliver all other items, there is no concern that something will delay the Nochri from performing his mission on Friday and cause him to do it on Shabbos -- this concern exists only when it comes to delivering mail. If the letter is found in the hands of the Nochri on Shabbos, it will be clear to all that the letter was sent by a Jew, since it is written in the Jew's handwriting. In contrast, a pot or other item has no recognizable feature that would reveal who owns it, and therefore even if the Nochri ends up delivering it on Shabbos, there is no concern that it will be apparent that he is performing a job on behalf of a Jew. (MAGEN AVRAHAM, cited by MISHNAH BERURAH OC 247:1).
(b) The RAMBAM (Hilchos Shabbos 6:20, according to the first explanation of the Kesef Mishneh) explains that if the "Davar" is not known to be in the city (and the Jew did not offer payment to the Nochri), then the Nochri may not bring the letter even if he is able to reach the house closest to the boundary before Shabbos (as Rashi explains). The Rambam, though, explains that a "Davar" is the official mail-courier, and he is in the same city as the Jew who sends the letter. The Nochri must be able to reach the farthest house in that town (the town from which the mail was sent), because it is not known exactly where the mailman lives. The Nochri must have time to reach the farthest possible house in case that is where the mailman lives. When the mailman is not known to be in town, then the Nochri must have enough time to reach the addressee himself (and not just the "Davar") before Shabbos in order for the Jew to be permitted to send the letter with him.
Again, only with regard to delivering a letter are we concerned that the mailman will not be in town. We are not concerned when sending other items (because of the reasoning of the Magen Avraham, as mentioned above).
(c) RABEINU CHANANEL explains that a "Davar" is a mailman who is in the same city as the sender (as the Rambam explains). However, Rabeinu Chananel says that when the mailman is not in the city, one is permitted to send a letter with a Nochri if there is enough time for the Nochri to reach the house closest to the boundary of the city of the addressee. If there is a mailman in town, then the letter may be sent with the Nochri even if he will not be able reach the house closest to the boundary of the addressee's town before Shabbos. If there is a mailman in town, one may give the letter to the Nochri to deliver immediately before Shabbos, since the Nochri is already within the borders of the town of his destination (i.e. the "Davar" to whom the Nochri is bringing the letter).
According to Rabeinu Chananel, the presence of a mailman in the sender's city makes the Halachah more lenient (and not that the absence of a mailman in the city makes the Halachah more stringent). (It seems that Rabeinu Chananel had a different text in his Gemara, because his explanation is difficult to reconcile with the text of our Gemara. -M. KORNFELD.)
2) HALACHAH: EMBARKING ON A JOURNEY BEFORE SHABBOS
OPINIONS: The Gemara cites a Beraisa which states that one may not embark on a sea voyage within three days prior to Shabbos. One may, however, embark on such a journey if it is for the sake of performing a Mitzvah.
The Rishonim give at least five different reasons for this prohibition (see MISHNAH BERURAH, introduction to OC 248):
(a) The BA'AL HA'ME'OR explains that it is forbidden to embark on a sea voyage before Shabbos because such travels are fraught with danger and one may have to desecrate Shabbos for the sake of Piku'ach Nefesh, saving his life. Even though Piku'ach Nefesh overrides the laws of Shabbos, nevertheless one may not purposefully enter a situation which may lead to the necessity to desecrate Shabbos.
(b) The RAMBAN (MILCHAMOS) argues with the Ba'al Ha'Me'or and maintains that it is not forbidden to enter a situation which may necessitate desecrating Shabbos for Piku'ach Nefesh. Rather, the reason why one may not embark on a journey prior to Shabbos is because the Nochri captain will be doing Melachah for the Jew on Shabbos when he ties up the sails, drops the anchor, etc.
(c) RABEINU CHANANEL writes that the Rabanan forbid traveling on a boat during Shabbos because of the prohibition of Techumin, traveling beyond one's 2000-Amah limit in any direction. (This decree applies only when the bottom of the boat is within ten Tefachim of the surface of the ground beneath the water. One is permitted to travel on the sea as far as he wants on Shabbos as long as he remains more than ten Tefachim above the ground.)
(d) The RIF says that the reason is because of the Mitzvah of Oneg Shabbos, experiencing pleasure on Shabbos, which one will lose when he goes on a sea voyage (due to the swaying of the boat and the different climate at sea). Embarking at least three days prior to Shabbos is permissible because it takes three days to become accustomed to the swaying of the boat and to the stale air at sea.
(e) TOSFOS (DH Ein Mafligin) explains that traveling on a boat on Shabbos is forbidden for the same reason that swimming is forbidden -- we fear that one might make a flotation device.
HALACHAH: Is it prohibited today to embark on a ship (such as a cruise ship) within three days prior to Shabbos?
Logically, all of the above reasons apply today, except for that of the Rabeinu Chananel (c). Therefore, it should be prohibited to embark on a sea voyage close to Shabbos. (See Insights to Nidah 38:5.)
3) BEIS SHAMAI "MADE A DECREE"
QUESTION: The Mishnah (17b) says that Beis Shamai agrees with Beis Hillel that on Friday, close to Shabbos, one may place the beams of the olive press and winepress atop the crushed fruits in order for the juice to be squeezed out on Shabbos. The Gemara asks why Beis Shamai "made a decree" to prohibit doing the other actions on Friday, while he did not make a decree to prohibit this one.
Why does the Gemara say that Beis Shamai "made a decree" to prohibit the other activities? The Gemara earlier (18a) says that those activities are forbidden mid'Oraisa because of the law of Shevisas Kelim!
(a) The RITVA, based on TOSFOS (18a, DH Leima), answers that the Gemara here is following the opinion of Rabah, who said (18a) that it is prohibited to put wheat in a watermill on Friday and let the mill operate on Shabbos, because the mill makes excessive noise which is disrespectful to Shabbos. Beis Shamai prohibits the other activities because of the concern that one may perform the activities on Shabbos itself, and not because of Shevisas Kelim.
(b) The Ritva rejects this explanation and offers a different one. When the Gemara says that they "made a decree," it does not mean that Beis Shamai made a decree, but that the Torah made a decree (of Shevisas Kelim) to prevent people from desecrating Shabbos. It is justified to call an act that is forbidden by the Torah a "decree."
4) THE OIL OF THE OLIVE PRESS WORKERS
OPINIONS: Rav and Shmuel argue whether the "oil of the olive press workers" is Muktzah on Shabbos. What is the "oil of the olive press workers"?
(a) RASHI explains that this is the oil that is left in the crevices or corners of the olive press. This leftover oil is usually given to the workers. Since the owner of the press has no intention to take the oil for himself because it is assumed that his workers will take it, it is Muktzah and may not be moved on Shabbos.
(b) TOSFOS argues that the fact that the oil does not belong to the owner (and he has no intention of taking it) does not cause the oil to become Muktzah.
Tosfos explains that the oil that Rav and Shmuel argue about is the oil that flows from olives that were placed under the press before Shabbos (in the case of the Mishnah). Since the oil was not accessible when Shabbos arrived (because it was underneath the heavy wooden press), when the oil flows out from the press on Shabbos it is prohibited because of Nolad. That is, it is considered something that came into existence on Shabbos.