According to the fatwas of the jurists, it is obligatory to learn the part of Sharia law that we often deal with. Also, a person must either be a mujtahid and derive the laws from evidence himself, or imitate a marja' of taqlid, or be certain through precaution that he has fulfilled his Sharia duty; for example, not doing an act that some mujtahids consider haram and some permissible, or doing an act that some mujtahids consider obligatory and some permissible.