We believe that the Imams have authority, and that Allah has ordered people to obey them. They are witnesses for mankind, doors opening the way of Allah, guides to Him, guarding of His knowledge, interpreters of His revelation, pillars of His Unity, and custodians of His Wisdom. They are the cause of peace among the inhabitants of the earth, just as the stars are for the heavens. And so the prophet said:

My household is like the ark of Nuh; whosoever embarks upon it will be saved, and hoover turns away from it will be drowned.

In accordance with the Qur'an, the Imams are:

Honoured servants who speak not until He has spoken and act by His Command. (21;26-7)

those whom he has kept away from uncleanness and cleansed with a thorough cleansing.

We believe that their orders and prohibitors are Allah's orders and prohibitions, that obedience and disobedience to them, friendship or enmity towards them, are all the same as if towards Allah. It is a sin to deny them, for everyone who denies them in fact denies the Messenger, and that is the same as denying Allah.

It is incumbent on all people to submit themselves to the Imams, to follow their commandments and to obey their sayings. So we believe that all commandments must be learned from their pure teachings, and that if one refers to another person concerning a commandment of the din, one will not be cleared of responsibility towards Allah and will not be sure that he has correctly performed his duty. Like the ark of Nuh, everyone who goes on board is saved, but whose who remain behind are drowned in the stormy sea of doubt, wandering, pretension and strife.

We do not seek at this time to prove that they were the legal khulafah' and that they possessed Divine authority, because this is not the place to do so, and discussing this question cannot bring back times gone by, nor restore things to their rightful owners. We only mean to show that we are obliged to refer to them to obtain the Divine commandments and to find out what the prophet truly said.

The path of those who were not educated by the Imams, or whose minds are not enlightened by knowledge of the Imams is in deviation from the straight path of Islam,and such a person will never be sure that his is free from the obligations and necessary duties that were revealed by Allah; for, granted that there are differences in opinion between Muslim groups as regards the commandments of the din, and that there is no hope that they will agree with each other to consider each one until one gains positive assurance of the truth from one of them and is sure that he is doing what Allah commanded him to do. For if one is under an obligation, one must clear oneself of that obligation with certainty through rational means.
Clear reasoning thus obliges one to refer to the Household of the Prophet. We must refer to them concerning Islamic doctrine and legislation as they were revealed to the Prophet. The prophet said:

I leave two great and precious things among you; the Book of Allah and my Household. If you keep hold of both of them,you will never go astray after me. One of them is greater than the other. The Book of Allah is like a rope hanging from heaven to earth, and the other is my Family and Household. Remember, these two will never be separated from each other until they encounter me a Kawthar (in Paradise).

This tradition is narrated by Sunni and Shi'a traditionalists alike. If you consider it carefully, you will be amazed and convinced by its good sense and by its excellent expression, because at first it says "if you keep hold of both of them, you will never go astray after me". What the Prophet left among us were two worthy things; together be considered them to be one, and he did not say that one only hold on to one of them, but that one should on to both of them so as to be misled. He explained the reason in the next phrase very clearly : "these two will never be separated from each other until they encounter me at kawthar". So, if a man separates from separates them and takes hold of only one of them, he will never be rightly guided. So they are the ship of Nuh, and peace for the inhabitants of the inhabitants of the earth. All those who do not take refuge with them will be drowned in the depths of perdition.

It is not correct to say that the meaning of this tradition is that it is necessary merely to love the Household of the Prophet, without following and obeying them, no-one can apply this interpretation unless he be a fanatic or totally ignorant,because this is in incorrect interpretation of the Arabic sentence.