Brit Milah (which means "Convenant of Circumcision"), also pronounced Bris Milah is a Jewish ceremony in which infant Jewish boys are brought into the covenant commanded by God to Abraham over 3,700 years ago, through ritual circumcision performed by a Mohel.
The Brit Milah has been carried out faithfully, from generation to generation, even during times of religious and ethnic persecution when Jews were forced to practice their rituals in secret. The only time the Jewish people willingly desisted from this practice was during the 40 years of wandering in the Sinai wilderness. Before entering Canaan, every male was circumcised by Joshua.
According to the Bible, Circumcision is a token of the convenant concluded between God, Abraham and his descendants (the people of Israel) for all generations.
The penalty for not having a Brit Milah was karet, excision from the people.
In order to convert to Judaism, one must undergo circumcision. Until then, one can not partake in the Passover offering or marry into a Jewish family.
The origins of the Brit Milah Mitzvah are found in the book of Genesis where God appeared to Abraham when he was 99 years old and commanded him to circumcise himself, his son, Ishmael, all the males of his household and all his slaves:
The following year, when Isaac was born, he was circumcised on the eighth day. In return for his faithfulness, God promised Abraham that his descendants would become a great nation and inherit the land of Canaan for eternity.
Because Abraham circumcised Isaac when he was eighth days old, a Brit is usually scheduled to that age, between sunrise and sunset. Brit Milah cannot be performed at night or before the eight day, and is considered invalid if done so. The day of birth counts as the first day.
If a baby is born bain hashemashot, during the period of twilight prior to nightfall, specific laws apply, especially preceding Shabbat or a festival. In such cases, the Mohel will determine the day, with rabbinic input, if necessary.