Halakhah do Rodzaju 34:25

When a brit milah (circumcision) takes place later than the eighth day of a boy’s life (such as a baby who could not tolerate a brit on the eighth day due to health reasons, or a non-Jew who wishes to convert),⁷Of course, none of these concerns applies when circumcising a baby on the eighth day of his life, as circumcision on the eighth day overrides Shabbat. The Gemara discusses the laws of a circumcision on Shabbat at great length in the nineteenth chapter of Masechet Shabbat. the Tashbetz (1:21) forbids performing it on a Thursday. He notes that on the third day after a brit (including the day of the brit), the baby is presumed to be in tremendous pain (see Bereishit 34:25 and Rashbam ad loc.). Thus, a baby who underwent a brit milah on Thursday may require medical treatment that will entail transgressing Shabbat (see Shabbat 86a). According to the Taz (Yoreh Deah 262:3), this problem exists when circumcising on Friday, too, as the baby suffers pain every day through the third day.⁸The Taz indicates concern for the baby’s pain and suffering per se, not for the desecration of Shabbat that it might necessitate. Apparently, he understands the problem of circumcising close to Shabbat in the same manner that the Rif explains the prohibition against traveling before Shabbat - concern for causing unnecessary discomfort during Shabbat (see Teshuvot Tzitz Eliezer 12:43). The Shach (Yoreh Deah 266:18) notes that some Rishonim do indeed assume that the baby suffers through the third day, but the Tashbetz explicitly permits circumcising on Friday even when it is not the eighth day.⁹See, however, Teshuvot Yabia Omer, Y.D. 5:23.

See also R. Ovadiah Yosef, Yabi'a Omer, II, Yoreh De'ah, no. 17, sec. 2, who maintains that the culpability of minors is a matter of dispute between Rosh and Rashi: Teshuvot ha-Rosh, klal 16, no. 1, states that the age of legal capacity is a matter of halakhah le-Mosheh me-Sinai, i.e., transmitted orally to Moses on Mt. Sinai as one of the many shi'urim or specifications of quantity and size with regard to precepts and transgressions, all of which were transmitted in this manner. Rambam, Hilkhot Melakhim 5:10, states that such shi'urim pertain only to commandments binding upon Jews but not to Noachide obligations. Thus Noachides are culpable for eating even a minute particle of flesh torn from a living animal while Jews are culpable only upon consumption of a quantity of food equal to the size of an olive. [Cf., however, Maharit Algazi, Kehillat Ya'akov, s.v. ḥazi shi'ur, who maintains that Tosafot disagrees with this ruling.] Rashi, Avot 5:21 and Nazir 29b, however, states that the age of religious majority is rooted upon the principle that a person is not a "man" until he reaches the age of thirteen as evidenced by the scriptural description, "And the two sons of Jacob, Simon and Levi, took each man his sword" (Genesis 34:25). Levi, at the time, was thirteen years old. The definition of the term "man" is a concept applicable to Noachides as well as to Jews. Rambam exempts Noachide minors from punishment, argues Rabbi Yosef, because he is in agreement with Rashi that exclusion of minors from culpability is a matter of definition rather than of shi'ur.