Brit milah literally means "covenant of circumcision". This covenant is between G-d and the Jewish people. The Torah tells the story of G-d saying to Abraham: "I will establish My covenant between Me and you and your children after you, throughout all generations, as an everlasting covenant, to be your G-d and your children's after you ... This is My covenant which you shall keep ... every male among you shall be circumcised. And you shall be circumcised in the flesh of your foreskin; and it shall be a sign of a covenant between Me and you." (Genesis XVII, 7-11).
In modern times the expression "every male among you" is taken to mean every Jewish male among you. Circumcision does not make a male child Jewish; he is Jewish if his birth parent is Jewish or had converted by the time of his birth. If a baby is not Jewish, he may have a brit as the first step of conversion.
In this case, if the child is to be raised as a Jew, the ceremony is called brit l'shem gerut and parallels the brit milah so closely that most attendees will not notice the difference. Brit l'shem gerut customarily is performed on the eighth day of the boy's life, but a later date is acceptable under halacha (Jewish religious law). Brit l'shem gerut frequently is used for adoptees and when the birth results from surrogacy. While no witnesses are required for brit milah, brit l'shem gerut requires the presence of two adult Jewish witnesses who are not related to the baby.
Every Jewish parent is obligated to circumcise his own son, just as Abraham circumcised his own son, Isaac. However, because most parents are not versed in the Jewish laws concerning brit milah, nor are they trained to circumcise, a mohel is normally asked to serve as the parent's stand-in. A mohel (or mohelet) is a righteous Jew who has received intensive instruction in the halakah (laws), minhagim (customs), brit (entry of a child into the covenant), and milah (surgical technique of circumcision). Any observant Jew who has mastered these skills may become a mohel; one need not be a physician, nor a rabbi. Historically, a mohel is considered so vital to a Jewish community that a scholar is forbidden to live in a community that does not have a mohel.
Eight days old is the age at which G-d commanded the Jewish people to circumcise their male children - "he that is eight days old shall be circumcised among you, every male throughout your generation ..." (Genesis XVII, 12). This mitzvah is so extraordinary that it can supersede the 'Laws of Shabbat' that normally prohibit such an operation on Shabbat and holidays. A brit may only take place during daylight hours; the earlier the better since we are eager to fulfill a mitzvah (commandment). The day of birth is counted as the first day, assuming the child is born before sundown. If he is born after sundown the following day is the first day of life.
Only certain circumstances justify the delay of a brit. Above all, a child that is not well may not be circumcised. Another exception is that, if the eighth day falls on Shabbat, but your son was born by cesarean section, the brit is delayed until the next day (Sunday). You should not delay a brit for convenience nor may it take place before the eighth day. If a brit is delayed for any reason, it may not take place on Shabbat or a holiday.
Traditionally, a brit was held in the synagogue to add beauty and sanctity to the mitzvah. Most parents prefer that a brit take place at home. The home is generally a warm, familiar environment. However, the brit may take place anywhere, as long as it is in a well-lit room large enough to accommodate all who are present..
If the eighth day falls on Shabbat or holiday, it is appropriate that the brit take place in a synagogue. In this way, it is appropriate for those attending the brit to travel, as they are doing so to daven (pray). However, all supplies and food must be brought to the synagogue before the start of Shabbat so as not to carry on Shabbat. The brit may either take place immediately following the Torah service, but before the Torah is replaced, or it may take place after the completion of morning services