The Shi'a Imameya have four sources for legislation, and they believe all of them have come from one source, Allah the Great and Almighty:

1.The Holy Qur'an ( The Book of Allah ) : The main and the first source.

2.Sunnah : It the saying and the deed  of the infallible (p.b.u.h).

3.consensus (of Moslem legal scholars): that show the opinion of the infallible.

4.Mind : if it decided a final decision about a certain matter, then such decision will be an evidence.

The Holy Qur'an :

It is the Book of Allah, which He descended on his servant and His messenger, the Prophet Muhammad (p.b.u.h) to be eternal miracle , and a source of guidance for the people to reform their affairs. It is the first source for the Islamic laws. Its verses are not limited on the  practical judgments, but it discussed various subjects, only one part of the Holy Qur'an is concerned by judgments, which consists of five hundreds verses. Scholars have compiled many books about the verses of the holy Qur'an, such as the verses of judgments by Al Muqadas Al Ardabili, and Kanzul Erfan by Al Muqdad, and many other scholars.

The Holy Qur'an which is between our hands today is the same one which is descended on the holy Prophet with the same words and same style, nothing has been added nor omitted. This fact is proved by the verse : {And this Qur'an is not such as could be forged by those beside Allah}[59]

There is no dispute that it is an evidence upon each male or female Muslim. Because of the following reasons :

being positive about its coming from the Prophet (p.bu.h) through the recurrent transmission a generation by another.

it sure that the Holy Qur'an is related to Allah the Great and Almighty, it is a miracle because of its method, meanings and its challenging to the eloquent of its time, who failed to go along with it. And proving its telling about  the unseen events.

As for its semantics, they are presumptive since it contains both precise and similar. For example the following verse:

{He is Who has revealed the Book to you, some of its verses are decisive, they are the basis of the Book, and others are allegorical, then as for those in whose hearts there is perversity, they follow the part of it which is allegorical, seeking to mislead, and seeking to give it ( their own ) interpretation, but none knows its interpretation except Allah,  and those who are firmly rooted in knowledge say: We believe in it, it is all from our Lord, and none do mind except those having understanding.}[60]

It also contains common and particular, abrogated and abrogation, brief and detailed verses. All which made the semantics of the holy Qur'an are supposition like the other evidences.

The evidences from Sunnah and the consensus (of Moslem legal scholars) are conditioned by checking the opposite ones and the other clear contexts.

As for the proof of the literal meaning of the holy Qur'an, the experts have concluded it through the verses and the narrations.

{So have We made it easy in your tongue that they may be mindful.}[61]

{Do they not then reflect on th Qur'an? Nay, on the hearts there are locks}[62]

{And most surly this is a revelation from the Lord of the worlds. The faithful Spirit has descended with it. Upon your heart that you may be of the warners. In a plain Arabic language}[63]

{And certainly we have made the Qur'an easy for remembrance , but is there anyone who will mind?}[64]

These verses declare frankly that, Allah the Great and Alighty has made the Qur'an easy for His servant and His Prophet, in its language and method, it doesn’t differ from the other phenomena of the Arabic speech.

As for the narrations, we mention the narration of Abdul A'ala for example: He asked about the judgment of someone who stumbled and lost his nail , then he put a gallbladder on top of it. Imam (p.b.u.h) answered him: "This matter the like ones are found in the Holy Qur'an: {and has not laid upon you any hardship in religion}[65], then he said to him: "wipe it "" the Imam told him such matters need no questions, since they are found in the external sense of the holy Qur'an.[66]

As for the proof of the Holy Qur'an, it is concluded through different ways, some of them are :

The saying of Ameerul Mu'mineen (p.b.u.h): " Allah has descended the Holy Qur'an up on the holy Prophet (p.b.u.h) to be a guidance and a mercy for people, the Holy Qur'an is the proof of Allah upon His creatures, and took their covenant ".

The other one is the narration of Thaqulain from the Prophet of Allah (p.b.u.h) : " as long as you hold on them you will not go astray"

Another one is the numerous narrations which command to compare every single narration with the Holy Qur'an, so if the narration agreed with the Holy Qur'an, then take it, otherwise leave it.

The Sunnah:

It is the second source of Islamic legislation after the Holy Qur'an, which means the saying and the action of the Prophet and t he infallible Imams (p.b.u.h)

The Sunnah is more general than the speech and the action of the infallible , it is divided into several parts:

Al Mustafeedh: The narration that is reported by more than one narrator, but it never reach the recurrence level ( tewator).

Motawater: It is the Prophetic narration which is reported by a number of narrators  that are not supposed to agree to tall false narrations.

Sahih ( the true ) : It is the narration which is narrated by a chain of validating narrators and they should be all from the Shi'a the twelfth.

Hassan ( Good Hadith ) : If its chain of transition was all from the Shi'a Imamiya.

Muawthak ( the proved) : If all or some of the chain of transition were not from the Shi'a the Imamiya.

As for the action ( of the infallible ), it is considered an evidence in general, and it supports the legal opinion in some situations. As for the daily actions such as eating, drinking and so on, there is no need to the action of the infallible Imam to  prove their lawfulness , since it is already proved by the mind and the Shari'a. But in another situation, when the infallible Imam leave a certain deed, that means it is not obligated, but if he did something partially that means it is not forbidden, unless he just did it to avoid the revenge.

As for ( Taqreer ): It means, the agreement of the infallible Imam when sees or knows about something that is done by someone or some people.

This holy Sunnah should be followed as the holy verse says :

{ and whatever the Apostle gives you, accept it, and from whatever he forbids you, keep back, and be careful of ( your duty to ) Allah; surely Allah is severe in retributing ( evil ) } [67]

{ and whoever obeys Allah and His Apostle, He will cause him to enter gardens beneath which rivers flow, to abide in them; and this is the great achievement.} [68]

{ certainly you have in the Apostle of Allah an excellent exemplar for him who hopes in Allah and the later day and remembers Allah much.}[69]

{ nor does he speak out of desire. It is naught but revelation that is revealed} [70]

This verse proves the argument of the Prophet's (p.b.u.h)  saying or agreement.

As for the sunnah of the infallible Imams ( p.b), whom – We ( the Shi'a) believe in  -  it taken from the holy Qur'an and the Prophetic Sunnah. And the following are some concise evidences:

The Holy Qur'an :

The verse of Tat-heer (disinfection) :

{O people of the House! And to purify you a ( through ) purifying}[71]

The verse refers to infallibility of the People of the House ( p.b) according to the Prophet (p.b.u.h) : "They are Imam Ali , the Lady Fatimah, Imam Hassan and Imam Hussein."

Thus, the meaning of the verse refers that the deeds, sayings but even thoughts of the People of the House were infallible of sins by the God's will. So the Sunnah of the People of the House is proved.

Hadith :
 
Hadith Al Thaqalayn: It is the most spreading among the prophetic narrations and its chain of transmission is the most trueness. It is :

"I am leaving the two heavies among you, the Book of Allah and the People of my House, as long as you keep with them, you will not go astray" [72]

In this narration the prophet coupled the Holy Qur'an and the People of the House,

The pure progeny as well as the holy Qur'an are far above the false, and as the holy Qur'an is the source of the legislation, the People of the House are also another source for legislations, and as the Holy Qur'an is purified and infallible, the People of the House are also purified and infallible , and as the Holy Qur'an is an evidence upon us, the People of the House are also an evidence upon us by their sayings and deeds.

Hadith Al Safinah:

"The People of my House among you are like Nuh's Ship, he who goes by it is saved, and he who stayed behind it is drowned."[73]

This narration means that following the People of the House is saving and causes the blessing of Allah the Great and Almighty.

Another narration says: "Stars are safety for the inhabitants of the Earth from drowning, and the People of my House are safety for my people from disagreement, so if any clan disagreed with them the will be the party of the Satan." [74]

We satisfied by this concise of verses and narrations of the Holy Prophet and His purified people of the House ( p.b)

Ejma' (consensus (of Moslem legal scholars)):
 
Ejma' is the third evidence that Muslim jurists use to deduce the legal opinion, and that should be through the saying of the infallible about an opinion, so Ejma' is not an evidence standing by itself in the opposite of the three evidences: The holy Qur'an, the sunnah and mind. So Ejma' is just revealing of the legal opinion. Ejma' has number of various definitions, such as :

Ejma': is the agreement of the Medina scholars.

Ejma': is the agreement of the Mecca and Medina scholars.

Ejma': is the agreement of the respectable scholars of the Umma 

Ejma': Is the agreement of the Umma of the Prophet Muhammad ( p.b.u.h) including the saying of the infallible ( p.b.u.h) .  

As for us, the Shi'a the Imamiya , we mean by the Ejma' if and only if those who agreed about an opinion including the saying of the infallible Imam.

Allama Al Hilli has said: " We believe that Ejma' is an evidence since it involves the saying of the infallible, and the Ejma' of any group - weather it was big or small - is considered an evidence as far as it involve the saying of the infallible".

And Sayyed Murtadha said:

"If the evidence of Ejma' is considered because of the being the infallible among them, then such Ejma' is an evidence unless one or more disagreed including the Imam ".

Then the conclusion is that, Ejma' by itself is not an evidence – as the extorters of Caliphate has said - but it is so if and only if the infallible was among them, since the argument is the saying of the infallible not their saying, because there is no reference  for Umma after the Prophet ( p.b.u.h) but the Holy Qur'an and the pure progeny ( p.b).

How to ensure that, the unanimous include the Imam (p.b) :

knowledge: If hear his saying, but that is rally happens.

Intuition : To know about the Imam's saying through the unanimous, and that could be happened through sensed principles, or it could be happened through a group of people who never agree on wrong even with concern to the incident.

The Types of Ejma' :

Ejma' has number of types, we are going to mention some of them:

Simple Ejma': It is the unanimity of the scholars on one opinion, so that it could be used by the opinion of each one.

The Tashrufi Ejma': It is the means claim of agreement on a legal opinion depending on seeing the Imam the Hujja and hearing the opinion directly from Him.

The Muhasil Ejma': It is the unanimity that is ensured by the feeling, which results from from following the scholars' opinions about a certain problem, then their agreement about it.

The transmitted Ejma': It is the unanimity that is not ensured by feelings, but it is taken from another jurist that has obtained the unanimity by himself.

The Medraki Ejma': It is the agreement of the jurists about a certain issue, then ensuring their evidence on such issue. 

The Compound Ejma': It is agreement of the scholars' opinions depending on the evidences of their different opinions of those scholars. For example: When some scholars say that something is forbidden and another group say that it is unpleasant, then there will be consensus (of Moslem legal scholars) that it is not obligated, desired nor allowed.

The Lutfi Ejma': Which refers to the basic of Lutf.

Dukhuli Ejma': We consider this kind of Ejma' an evidence because in involves the infallible (p.b.u.h) in a certain way. Since the consensus (of Moslem legal scholars) or the Umma is invalid unless the infallible is among them. So the cause of the evidence of such Ejma' is the involvement of the infallible .

Mind :
 
Mind is considered one of the evidences or the legal sources for the legal opinions, and studying it causes to study the good and the ugly and their different meanings. So to study "Mind" it should be divided into two kinds: theoretical and practical, and speaking about legal opinions leads us to study the concept of the "inherence rule": I mean: whatever was agreed by mind, it is agreed by religion. And that shows the position of the mind as one of the four evidences, so we can say in short:

Mind has it own way to study the jurisprudence and its principles, and many of jurists and scholars has depended upon the judgment of mind to solve many problems such as :

The  mentality innocence: It means the ugliness of punishment without evidences. Scholars depended on it to cancel the suspected judgment and not to punish depending on it.

The inherence between commanding something and prohibiting its opposite : For example, if someone saw an impurity in a mosque, he is charged with removing it , so if  he didn’t remove it and did his prayer, then his prayer was not excepted.

Doing the most important matters before the less important ones in case of competition.

The necessity of the premise of the obligation.

So, those are the sources of the Islamic legislation.

---

[59]  Yunis : 37
[60]  Aal Emran: 7
[61]  Al Dukhan: 58
[62]  Muhammad: 24
[63]  Al Shu'ara': 192-195
[64]  Al Qamar: 17
[65]  Al Hajj : 78
[66]  page 60 , Alhukm
[67]  Al Hashr : 7
[68]  Al Nisa : 13
[69]  Al Ahzab: 21
[70]  Al Najm : 3,4
[71]  Al Ahzab: 33
[72]  See : Sahih Al Turmdi: page 66
[73]  Al Hukm Al Shar'I : page 66
[74]  The same reference.