Mishneh Torah (Rambam) משנה תורה

Circumcision may be performed by anyone. Even a person who is himself not circumcised, a slave, a woman, or a minor may perform the circumcision, if an adult male is not present. A gentile, however, should not be allowed to perform the circumcision at all. Nevertheless, if he does so, there is no need for a second circumcision. Any utensil may be used for circumcision, even a flint, glass, or any article that cuts. One should not circumcise with the sharpened side of a reed, because of the danger involved. The optimum manner of performing the mitzvah is to use an iron utensil - either scissors or a knife. Throughout the Jewish community, it has become customary to use a knife.

How is the circumcision performed? The foreskin that covers the crown of the penis is cut off until the entire crown is revealed. [This step is referred to as milah.] Afterwards, the soft membrane that is beneath the skin should be split along the mid-line with one's nails and peeled back to either side until the flesh of the crown is revealed. [This step is referred to as pri'ah.] Afterwards, one should suck the place of the circumcision until all the blood in the further reaches is extracted, lest a dangerous situation arise. [This step is referred to as metzitzah.] Any [mohel] who does not perform metzitzah should be removed from his position. After one has performed metzitzah, one should apply a bandage, a compress, or the like.

There are strands of flesh that disqualify a circumcision [if they are not removed], and strands of flesh that do not disqualify a circumcision. What is implied? If, [after circumcision,] a portion of the foreskin is left that covers the majority of the crown of the penis' height, the child is considered to be uncircumcised, and this flesh is considered a tzitz that disqualifies the circumcision.If only a small portion of flesh remains which does not cover the majority of the crown of the penis' height, it is considered to be a tzitz that does not disqualify the circumcision.

While the person performing the circumcision is involved in the operation, he should go back and remove both the tzitzim that disqualify the circumcision and the tzitzim that do not disqualify the circumcision. Once he has interrupted his activity, he must return and remove any tzitzim that disqualify the circumcision, but he does not return to remove anytzitzim that do not disqualify the circumcision. When one performs a circumcision without performing pri'ah, it is considered as if the circumcision was not performed.

[The following ruling is given when] a child's flesh is soft and hangs loosely, or if he is very fat and, therefore, it appears that he is not circumcised. We should observe him when he has an erection: if he appears circumcised at that time, it is unnecessary to do anything more. One must, however, correct the flesh on the sides, because of the appearance it creates. If, however, he does not appear to be circumcised when he has an erection, the loose hanging flesh on the sides should be cut off until the crown of the penis is revealed while it is erect. This was ordained by the Rabbis. According to the Torah itself, even though he [appears] uncircumcised, since he was circumcised once, there is no obligation to circumcise him again.

Anything that is necessary for the circumcision [itself] may be performed on the Sabbath. We may perform milah, pri'ah, and metzitzah, return and remove the tzitzim that disqualify the circumcision even though one has interrupted one's activity, return and remove the tzitzim that do not disqualify the circumcision if one has not interrupted one's activity, and bandage the circumcision afterwards. The preparation of articles that are necessary for the circumcision does not supersede the prohibitions against labor on the Sabbath. What is implied? If we are unable to find a knife, a knife may not be made on the Sabbath, nor may we bring it from place to place. It is even forbidden to bring it from one courtyard to another courtyard in an alleyway if there is no eruv. Although the [mitzvah of] eruv is only Rabbinic in origin, it is not superseded by [the necessity] to bring a knife, since it was possible to bring the knife on Friday.

Herbs may not be ground to [use for the compress], nor may water be heated [to wash the child], nor may a compress be prepared, nor may wine and oil be mixed [on the Sabbath itself]. If cumin was not ground on Friday, one may chew it on the Sabbath and apply it [to the wound]. If one did not mix wine and oil together, they may each be applied individually. This is the general rule: Whatever can be performed on Friday does not supersede [the prohibitions against labor on] the Sabbath. Should one forget and not prepare the accessories necessary for the circumcision, the circumcision should be performed on the ninth day.

If a child was circumcised on the Sabbath and, afterwards, the hot water was spilled or the herbs [for the compress] were scattered, one may do anything that is necessary for him on the Sabbath, because of the danger involved. In a place where it is customary to wash a child, he may be washed on the Sabbath on the day of his circumcision, both before the circumcision and after the circumcision, and on the third day of his circumcision. The child's entire body may be washed as well as the place of the circumcision itself. [On the third day,] he may be washed with water that was heated on Friday or with water that was heated on the Sabbath itself, because the situation involves danger.

If a knife was forgotten and not brought [to the place of the circumcision] on Friday, one may instruct a gentile to bring it on the Sabbath, provided he does not bring it through the public domain. The general principle governing this matter is: It is permissible to tell a gentile to perform any activity that we are forbidden to perform as a sh'vut, so that we may perform a mitzvah at its appropriate time. When, however, an activity is prohibited because a forbidden labor is involved, we may not instruct a gentile to do it [for us] on the Sabbath.

[The preparation of] the accessories for circumcision - even when the circumcision is being performed at the appropriate time - does not supersede [the prohibitions against labor on] the holidays, because it is possible to complete them before the commencement of the holiday. [This ruling can be derived through the following] process of inference: If [the preparation of] the accessories for circumcision is not significant enough to supersede the Rabbinic prohibitions of sh'vut, why should they supersede a negative commandment of the Torah? [Nevertheless, there are certain greater leniencies on festivals:] One may grind herbs for [the compress], since these herbs are fit to be used in food. Similarly, oil and wine may be mixed together.