^4.See Mikra’ei Kodesh (Harari) 5:11 (pp. 101-107), which specifies the uncertainty and outlines the custom of each city. There are two possible reasons for uncertainty: 1) whether the city had a wall at the time of Yehoshua bin Nun (and even if it did, perhaps the wall was erected after the houses were built); 2) whether the city is currently located in the same place as in ancient times. Some cities are uncertain for both reasons, while others are uncertain for only one reason. The cities enumerated in the first list were more likely surrounded by a wall, while for those in the second list this were less likely. Consequently, fewer people customarily read the Megilla on the fifteenth in those places.
^ 5.Megilla 5b relates that the amora Ĥizkiya read the Megilla in Tiberias on both the fourteenth and the fifteenth, because although the city was walled on three sides, the fourth side bordered on the sea, and thus it was uncertain whether the city was considered walled. In addition, R. Asi read the Megilla in Hutzal on both the fourteenth and the fifteenth, because it was uncertain whether it was walled at the time of Yehoshua bin Nun.
According to Ramban, Rashba, Ran, and Ritva, based on the Ge’onim, those who live in cities of uncertain status read the Megilla exclusively on the fourteenth, with a berakha. Technically, they do not need to read the Megilla at all, because we are lenient in cases of uncertainty about a rabbinic law. However, in order to avoid canceling the mitzva altogether for such people, the Sages established that they read it on the fourteenth, like the majority of the world. Ĥizkiya and R. Asi were merely following a pious custom by reading it on the fifteenth as well. In contrast to the Rishonim mentioned above, Rambam, Shibolei Ha-leket, Me’iri, and SA 688:4 maintain that halakha requires residents of cities of uncertain status to read the Megilla on both days – on the first day with a berakha and on the second day without a berakha. (According to Ri’az, they recite a berakha on both days, while according to R. Yeĥiel, they omit the berakha both days.)
Seemingly, one could ask: How can these people recite a berakha over the Megilla reading on the fourteenth when it is uncertain if their city is considered unwalled? The answer is that the Yerushalmi (y. Megilla 1:1, 1:3, 2:3) states that, be-di’avad, a resident of a walled city who reads the Megilla on the fourteenth fulfills his obligation. It is true that Pri Ĥadash §688 and several other Aĥaronim state that the Bavli disagrees with this, and according to them, a resident of a walled city who reads the Megilla on the fourteenth does not fulfill his obligation. Nonetheless, Pri Megadim, Mishbetzot Zahav 688:2 and other Aĥaronim maintain that the Bavli agrees with the Yerushalmi. In addition, Vilna Gaon 688:4 explains that this is the basis for the opinion of Rambam and SA. This is also how the position of Ramban and Rashba is explained. Therefore, residents of uncertain cities read the Megilla on the fourteenth, with a berakha.
Rashba, Ritva, and the Vilna Gaon write that the practice of reading the Megilla on both days in uncertain cities applies only in Eretz Yisrael. Others disagree; see MA 688:4. Ben Ish Ĥai (Tetzaveh 14) states that in Baghdad the custom was to read the Megilla on both days.
According to Ri’az and MA 688:5, when there is uncertainty regarding a city’s status, its residents observe all the mitzvot of Purim on both days. Pri Ĥadash and Mateh Yehuda maintain that reading the Megilla is the only mitzva that is performed on both days. Binyan Shlomo explains that the mitzva of reading the Megilla was instituted by the prophets, while the other mitzvot were rabbinically mandated, which is why we are more lenient regarding the other mitzvot when there is an uncertainty. (See MB 688:10, which sides with MA, whereas BHL§695 agrees with Pri Ĥadash. Perhaps the distinction is that he rules leniently when it comes to mitzvot that require monetary outlay.) Igeret Ha-Purim states that the custom in Hebron and Tiberias is only to read the Megilla on the fifteenth, not to observe the other mitzvot. The author of Ben Ish Ĥai observed all of the mitzvot on both days. The Aĥaronim disagree about whether there is Torah reading (Kaf Ha-ĥayim 688:25). Regarding Al Ha-nisim, MB 693:6 states that one should recite it on the second day as well, while Kaf Ha-ĥayim 688:23 states, based on R. Ĥayim Vital, that one should not recite it.
^ 6.According to Birkei Yosef 688:9, cited in BHL 688:2, people who live near a city of uncertain status read the Megilla only on the fourteenth. Pe’at Ha-shulĥan 3:15 states that the villages near Tzefat read it on both days. Ĥazon Ish 153:3 concurs; for this reason, Ĥazon Ish required the residents of Bnei Brak, which is close to Jaffa, to read the Megilla on the fifteenth. However, we already learned that, according to many Rishonim, technically, one does not need to read the Megilla on the fifteenth even in places of uncertain status. Therefore, in a nearby village, there are two uncertainties (sfek sfeika), and so we rule leniently. In addition, perhaps one could claim that this strengthens the opinion that even in the city of uncertain status itself the Megilla should be read only on the fourteenth. After all, one of the explanations given for why a place adjacent to a walled city takes on the status of the city is that we want to avoid separating between people who live as neighbors (Turei Even and Ĥatam Sofer, as cited above in n. 3). If residents of a place adjacent to a city of uncertain status would celebrate Purim only on the fourteenth, while the residents of the city itself celebrate on the fifteenth as well, they will be divided. Therefore, it is proper for residents of the uncertain place to follow the practice of those who live adjacent to them and observe only the fourteenth, especially since most Rishonim (based on the Ge’onim) espouse this opinion.