Shafaqna (Shia International News Association) – The Grand Ayatollah Sistani answered a question regarding Mujtahid.According to Shafaqna the question and answer is as follows:
Question: Why is it necessary to follow?
Answer: It is necessary for a Muslim to believe in the fundamentals of faith with his own insight and understanding, and he cannot follow anyone in this respect i.e. he cannot accept the word of another who knows, simply because he has said it. However, one who has faith in the true tenets of Islam, and manifests it by his deeds, is a Muslim and Mo’min, even if he is not very profound, and the laws related to a Muslim will hold good for him. In matters of religious laws, apart from the ones clearly defined, or ones which are indisputable, a person must act according to the verdicts (Fatwa) of the most learned Mujtahid.
Imam Mahdi: هم حجتی علیکم و انا حجة الله علیهم. Meaning, they (the jurisprudents) are our proofs on you and I am the proof of God. Also there is another tradition from the Ma’usoom which says, (من کان من الفقهاء صائنا لنفسه مخالفا لهواه مطیعا لامر مولاه فللعوام ان یقلدوه) meaning, ordinary people should follow a jurist who guards himself against temptations and sins and who is pious and obedient to the commands of his Lord.
Source: Ayatollah Sistani