QUESTION: The Gemara discusses a case in which a person has two babies that need Milah. One baby's Milah is to be performed on Shabbos and the other baby's Milah is to be performed on Sunday. The Mohel mistakenly circumcises on Shabbos the baby whose Milah was supposed to be on Sunday. The Mishnah says that he is Chayav for performing a Melachah on Shabbos.
Why is he Chayav? Since he performed the Milah before the eighth day, he did not fulfill the Mitzvah of Milah, and thus his act is Mekalkel, a destructive act and not a productive one (see Shabbos 106a). One is normally exempt from a Korban if he performs a destructive Melachah (Mekalkel) on Shabbos!
(a) REBBI AKIVA EIGER cites the ROSH (#5) who proves that if Milah is done to a baby before the eighth day, the baby does not need any further Milah or Hatafas Dam Bris when the eighth day arrives. Although the Mitzvah of Milah was not fulfilled, the baby is considered fully circumcised. Accordingly, the act of Milah was indeed a constructive one.
(b) Rebbi Akiva Eiger further explains that from the Gemara in Kerisus (19b) it is evident that the Mishnah here follows the opinion of Rebbi Shimon, who maintains that one is Chayav for the Melachah of Chovel (making a wound) even when his act is Mekalkel.
QUESTION: The Mishnah says that it is possible for the time for a baby's Milah to occur twelve days after he is born.
If he was born Bein ha'Shemashos, we wait until the ninth day (out of doubt that Bein ha'Shemashos is considered night) to perform the Milah. If he was born during Bein ha'Shemashos of Erev Shabbos, the ninth day is Shabbos and we cannot perform the Milah on Shabbos when there is a doubt if that day is the eighth day. If the day after Shabbos is the first day of Rosh Hashanah, we must wait until after the two days of Rosh Hashanah to perform the Milah, and thus the Milah is performed on the twelfth day.
Why does the Mishnah say that Shabbos was followed by two days of Rosh Hashanah, and not by any two-day Yom Tov (of Yom Tov Sheni Shel Galuyos)?
(a) The RAMBAM (Hilchos Milah 1:15) infers from the Mishnah that a Milah that is not performed at its proper time (on the eighth day) does override the second day of a normal Yom Tov. If that day is a Yom Tov other than Rosh Hashanah, indeed the Milah is performed on the second day of Yom Tov.
The Rambam's reasoning is that the second day of Yom Tov is a rabbinical enactment, while the Mitzvah of Milah is mid'Oraisa. A Mitzvah mid'Oraisa overrides a Mitzvah d'Rabanan. The second day of Rosh Hashanah, however, is not merely a Yom Tov because of the rabbinical enactment. Rather, it is a Safek Yom Tov mid'Oraisa, and therefore one is not permitted to perform Milah on the second day of Rosh Hashanah when that Milah cannot be performed on Shabbos.
(b) The RITVA, TESHUVOS HA'ROSH, and TUR dispute the Rambam's ruling. They maintain that Milah (when not performed on the eighth day) may not be performed on the second day of any Yom Tov. The reason why the Mishnah specifically mentions Rosh Hashanah is because the Mishnah was written in Eretz Yisrael, where there was no other Yom Tov that was two days long. This also seems to be the opinion of Rashi in Pesachim (47a).


OPINIONS: The Gemara says that Tzitzin ha'Me'akvin are strips of skin that cover "most of the height of the Atarah." What exactly is the Atarah?
(a) The BEIS YOSEF (YD 264) quotes a response written by "a Chacham from Spain" who writes that the Atarah is the entire upper section that is covered by the Orlah-skin before the Milah. The strips of skin that cover "most of the height of the Atarah" refer to long pieces of skin that cover the top of the organ until past the tip.
(b) RASHI, however, seems to understand the definition of the Atarah differently, as the BECHOR SHOR here points out. Rashi on the Mishnah (DH Atarah) implies that the Atarah is the ring of skin just below the Orlah that encircles the organ. The circumference of skin there is the Atarah. Accordingly, strips of skin that "cover most of the height of the Atarah" are strips that cover most of the height of that narrow ring of skin (that is, even very small strips of skin). The Bechor Shor supports Rashi's opinion with a Gemara in Yevamos (75a).
HALACHAH: The Beis Yosef writes that one should be stringent like the second opinion and make sure to cut off even small strips of skin that remain, if they cover most of the height of the circular ridge of skin.