1) HALACHAH: MAY A YOUNGER SIBLING MARRY BEFORE AN OLDER SIBLING?
OPINIONS: The Gemara points out that in the two places in the Torah where the daughters of Tzelofchad are mentioned, they are listed in different orders. The Gemara explains that in Parshas Pinchas (Bamidbar 27:1), the Torah lists them according to their wisdom, while in Parshas Mas'ei (Bamidbar 36:11), the Torah lists them according to their ages.
The RASHBAM (DH Lehalan) writes that it is logical to assume that the daughters married in the order of their ages, for we find that such a custom existed in ancient times. The Torah teaches that Lavan justified his deception of Yakov (when he stealthily gave him Leah in marriage and not Rachel) by saying that "it is not the custom in our place to marry off the younger before the older" (Bereishis 29:26).
Is the custom of giving precedence to the older sibling in marriage observed today?
(a) The Gemara states that the fact that in one place the Torah lists the daughters of Tzelofchad in the order of their wisdom, and in another place it lists them in the order of their ages, supports Rav Ami's statement that when a meeting is convened for the purpose of teaching Torah, the wisest scholar is honored first and is given the most prominent place. In contrast, in a festive meal, the oldest person present is honored first and is given the most prominent place. The Rashbam (DH b'Mesibah) adds that at a wedding, honor is given to the oldest participant.
The SHACH (YD 244:13) cites the BACH who explains that the preference of age at a wedding means that if brothers (or sisters) from the same family are getting married, the wedding of the older one should be made first, even though the younger one might be more advanced in wisdom.
(b) RAV MOSHE FEINSTEIN zt'l (in IGROS MOSHE EH 2:1) discusses a case in which the father of a young woman wanted his daughter to marry a young man from a certain family, even though the young man had an older brother who was not yet married and who was upset that his younger brother might get married first. Rav Moshe Feinstein cites the Bach who says that the younger brother must wait for his older brother to get married first. Rav Moshe Feinstein disagrees with this ruling, however, and maintains that the Bach refers only to a case in which both brothers are already engaged to be married. Only in such a case is the younger brother obligated to honor his older brother by letting him get married first. If, however, the older brother has no bride yet, then the younger brother is not obligated to wait for the older brother to get married. On the contrast, Rav Moshe Feinstein concludes, the younger brother should marry immediately in order to fulfill the Mitzvah of marrying and having children.
The daughters of Tzelofchad had all found their prospective husbands, and therefore they were married in order of age.
The TESHUVOS MAHARSHAM (3:136) also rules that a younger sister may marry before an older sister. He states that the practice mentioned by Lavan is not obligatory law, but rather an act of Derech Eretz and proper manners. The MINCHAS YITZCHAK (8:125) rules similarly, and writes that the young brother should marry first when it is not possible for the older brother to get married immediately. (Y. Marcus)

120b----------------------------------------120b

2) HALACHAH: THE QUALIFICATIONS OF A "DAYAN" WHO MAY ANNUL VOWS
OPINIONS: The Gemara derives from the verse that Hataras Nedarim, the annulment of vows, may be performed by Aharon, his sons, and by all of the Jewish people. Rav Acha bar Yakov infers from here that a Beis Din comprised of three laymen may annul a Neder. Although the Torah implies that a Neder may be annulled by any one of the leaders of the Shevatim (Bamidbar 30:2), Rav Chisda explains that this means that one who is an expert may annul a Neder on his own without the presence of two others.
1. What degree of expertise must a Dayan have in order to be qualified to annul vows on his own?
(a) The RASHBAM (DH Hachi Nami b'Yachid) writes that he must be an expert in Gemara, meaning a distinguished Rav who is capable of issuing Halachic rulings. This is also the view of the RAMBAM (Hilchos Shevu'os 6:5) who writes, "How are oaths annulled? The person who swore should come to a distinguished wise man, or to three laymen if there is no expert available."
(b) However, the RAN in Nedarim (23a, DH v'Heter Nedarim) cites the RAMBAN who writes that the expert must be one who has received Semichah, the ordination passed down personally through the generations from Moshe Rabeinu. Semichah is a higher qualification that just expertise in Gemara. The Ramban's source for this is the Gemara later (121a) which compares the expert Dayan who may annul a Neder by himself to the three expert Dayanim required to sanctify the new moon and declare Rosh Chodesh. Just as those three Dayanim must have Semichah, the single expert Dayan capable of annulling a Neder must also have Semichah. The RITVA (Nedarim 23a) writes that even Rav Nachman, a distinguished Dayan in the times of the Gemara, did not possess the appropriate Semichah for the annulment of vows, as is clear from the Gemara in the first Perek of Maseches Sanhedrin. (The Ritva's reference apparently is to Sanhedrin 14a, where the Gemara says that Semichah did not exist in Bavel, where Rav Nachman lived.)
2. When three laymen annul a Neder, what level of knowledge must they possess?
(a) The RAN in Nedarim maintains that although the laymen are not required to be expert in the Halachos of Nedarim, they nevertheless must be people capable of understanding those Halachos when explained to them.
(b) The RAMBAM, however, does not specify this as a qualification. The KESEF MISHNEH (Hilchos Shevu'os 6:1) states that the laymen qualify for Hataras Nedarim even when they are not capable of understanding the Halachos. The LECHEM MISHNEH (Hilchos Shevu'os 6:5) writes that even if the Halachah requires that these three Dayanim be capable of understanding the laws when explained to them, in practice they do not need to be capable of understanding the laws, since there is no one today who is capable of explaining the laws to them.
The SHULCHAN ARUCH (YD 228:1) and SHACH there (#2) rule that only laymen who are capable of understanding the laws of Nedarim when explained to them may serve as Dayanim to annul a Neder. The LEVUSH (cited by the Shach) rules that it suffices that they understand a little -- as much as it takes to know what vows they are annulling. They are not required to understand all of the Halachos well. (Y. Marcus)