Originally Posted by Zee

The main reason given is cleanliness. It is essential that every Muslim washes before praying.

It is important that no urine is left on the body.

Muslims believe the removal of the foreksin makes it easier to keep the penis clean because urine can't get trapped there.
Supporters of circumcision also argue that excrements may collect under the foreskin which may lead to fatal diseases such as cancer.

Some Muslims see circumcision as a preventive measure against infection and diseases.

Another thing I wish to make clear is:

Circumcision is not compulsory in Islam but it is an important ritual aimed at improving cleanliness. It is strongly encouraged but not enforced.