Wilayat is the most important issue after Prophethood for Muslims. The righteous Wilaya is the sine qua non for a true Islamic state. A lot of problems which Muslims face owe their origin to disregard for the righteous, just successors of the Prophet (peace be upon him and his progeny).
Martyr Ayatollah Murtadha Mutahhari explains Wilaya in the following manner: "The words, 'Wala, Walayat, Wilayat, Waly, Mawla, Awla' and the like have been derived from the same root, viz. Waly. The various forms of this root-word and its derivatives are the most oft-recurring words in the Holy Qur'an. The original meaning of this root-word as mentioned by Raghib in his lexicon 'Mufradatul Qur'an' is one thing taking place by the side of another in such a way that there is no distance between them i.e. if two things are placed side by side in such a manner that there is no other thing between them the root-word 'Waly' is used… this root-word is naturally used for nearness and proximity also, both physical and figurative. And again for this very reason it has been used in the sense of friendship, love, patronage, guardianship, control etc., because all these conceptions involve some sort of contact and proximity." (Master and Mastership)
Particularly in an Islamic context, Wilaya is the faculty of legal and moral authority, which enables a person in whom this authority is vested to exact obedience to fulfill the moral vision of Islamic revelation. The Islamic concept of Wilaya implies religious and political authorities are one and the same. Accordingly in the Qur'anic context of the divine guidance for humanity, the Prophet's role should be considered as the head of state and the founder of a religious order. The sense in which the Holy Qur'an speaks about the Wilaya of the Prophet is essentially the whole of human life, and not just a limited segment of it.
In his famous book The Master and Mastership, Ayatollah Mutahhari has presented four dimensions of Wilaya:
1) Wala of Love (Wila-e-Muhabbat): All Muslims are obliged to love and respect the Ahlul Bayt (peace be upon them). The Holy Qur'an says "Say: I ask you no reward for my preaching save love and affection toward my progeny." (42:23) Ayatollah Mutahhari explains: "This love is a prelude to all kinds of Wala prescribed by Islam. It binds the people to the Holy Family and gives us an opportunity to benefit from their teachings, practices and precepts."
Imam Shafi'i says in his famous verses: "Let everybody know that if the love of Muhammad's descendants means to be a Rafidi, I am a Rafidi." Imam Shafi'i also says, "O Ahlul Bayt! Allah has made it obligatory in the Qur'an to love you. It is a matter of pride for you that without invoking blessing on you, prayer is not valid." He also says, "After having seen that the people have chosen different ways which have led them to the Ocean of deviation and ignorance, I have, in the name of Allah, embarked the ship which may lead me to safety. The Ahlul Bayt of the Holy Prophet are that very ship. We have been ordered to hold fast the rope of Allah, and that rope is their love."
2) Wala of Imamat (Wila-e-Imamat): Ayatollah Mutahhari says, "Wala of Imamat signifies religious authority, i.e. a position which makes the Imam a model for others who have to follow him and take instructions from him. Such a position automatically implies the infallibility of the Imam. It is the same position about which the Holy Qur'an, while referring to the Holy Prophet, says:
'The Messenger of Allah is certainly a good example for those of you who have hope in Allah and believe in the Last Day and remember Allah very often.' (33:21)
'Say: If you love Allah, then follow me, Allah will love you and forgive you your faults, and Allah is Forgiving, Merciful.' (3:31)
This Wala reflects the power and authority of the Ahlul Bayt in guiding their followers in spiritual matters. According to a very famous hadith, the Holy Prophet has said, 'I am leaving behind among you two authorities: the Book of Allah and my Ahlul Bayt. They shall not be separated from each other 'til they arrive at the Fountain of Kawthar. If you go ahead of them or fall short of expectations, you shall be misled. Do not try to teach them, for they know better than you.'
That kind of religious leadership, which makes every word and action of the leader authoritative, is called Imamat. It is a sort of Wilayat in the sense that it implies a sort of control over the affairs of the people. This kind of Wala when used with reference to an Imam means religious authority and the right of leadership, and when used with reference to the Muslims, means the acknowledgement of this right."
3) Wala of Leadership (Wila-e-Zi'amat): This kind of Wala is concerned with the right of social and political leadership. According to Ayatollah Mutahhari: "Indeed a society must have a leader. The person qualified to take charge of the social affairs of the Muslims and to control their destinies is called Walyy-u Amr al-Muslimeen (Administrator of affairs of the Muslims). During his lifetime, Muhammad, the Prophet of Islam, held this position, which was granted to him by Allah. Following his death, it was attained by the Ahlul Bayt. There exists undeniable evidence to prove this fact. Besides the Hadith of Ghadeer, several verses of the Holy Qur'an point out this kind of Wala."
"O you who believe! Obey Allah and obey the Messenger and those in authority from among you; then if you quarrel about anything, refer it to Allah and the Messenger, if you believe in Allah and the last day; this is better and very good in the end." (4:59)
"The Prophet has more authority over the believers than that which they have over their selves." (33:06)
The Holy Prophet was the Imam, the religious leader and the law-giver. Whatever he said or did was authoritative. The Qur'an says: "If the Messenger orders you to do something, obey it, and if he forbids something abstain from it." (59:07)
His decisions with regard to any internal disputes and any lawsuits were binding and valid. Allah says in the Holy Qur'an to the Prophet: "I swear by your Lord, they will not be true believers until they make you judge of what is in dispute between them and find in themselves no dislike of that which you decide, and submit with full submission." (4:65)
The Prophet held political and social Wilayat. In addition to preaching and explaining the commands of Allah and arbitrating disputes among the Muslims, he also managed their social and political affairs. He was the Administrator of affairs of the Muslims, as shown in the following verse: "Obey Allah, His Messenger and those of you who are in charge of your affairs." (4:59)
This position of the Holy Prophet out of the three preceding positions – of Imam, religious leader, and law-giver – constitutes the basis of the question of Caliphate, and his successor has the same rights and status.
4) Wala of Control (Wila-e-Tasarruf): This dimension reflects universal power in which the Prophet and his Ahlul Bayt have been vested, by the grace of Almighty Allah. This is the highest stage of the Wilayat of Ahlul Bayt. Imamat and Wilayat in this sense signify the same position, though from different points of view.
This is an authority that makes it possible for the Wali to exercise his power over everything that exists. The authority and control of the Ahlul Bayt is vertical with respect to that of Allah. In the words of Ayatollah Imam Ruhollah Khomeini: "It is a vicegerency pertaining to the whole of creation, by virtue of which all the atoms in the universe humble themselves before the holder of authority." (Islamic Government: Governance of the Jurist)