Subject to overriding medical considerations, the circumcision must take place eight days after the birth of the child, even when this falls on "Shabbat". The child must be medically fit for a circumcision to be performed, and Jewish law prohibits parents having their son circumcised if medical doctors hold that the procedure may unduly threaten the child's health (e.g. because of hemophilia). If by reason of the child's debility or sickness the ceremony is postponed, it cannot take place on "Shabbat".