For the child to be considered Jewish, he or she must be formally converted. Such a conversion is an absolute requirement of Jewish law, and dispensing with it can have serious consequences later in life, for the child may reach Bar Mitzvah age, want to marry or join a synagogue, only to be told by a rabbi that he or she is not really Jewish. The ceremony is simple, and should be done as early as possible. If a boy has already been circumcised for medical reasons, a symbolic circumcision must be done. A drop of blood is taken from the side of the penis, a simple and painless procedure.
Immersion is a requirement for both boys and girls.
Usually the immersion takes place as soon as the infant is old enough so that there is no physical danger. Six months is the age preferred by many rabbis. The child should be naked and held in such a way that the water touches every part of the body. The child is then immersed once more. Who has sanctified us with His commandments and commanded us on the immersion.