Question: What is the minimum requirement for keeping a beard?
Answer: Shaving the beard is Haram based on obligatory precaution, and this includes the hair that grows on the sides of the face. However, there is no problem in shaving the hair that grows on the cheeks and the necks. The minimum requirement of beard should be as much as the custom norm (Urf) state that "this person has a beard", even if is for example trimmed to a beard size 3.
Ayatollah Al-Sayyid Ali Al-Husseini Al-Sistani