Linguistically Ijtihād is the exertion of ones utmost effort to realise a matter which entails a measure of discomfort and difficulty. As for the definition of the Usuli scholars, it is specifically the expenditure of ones energies in seeking a preponderant opinion (zann) about a thing from the Sharī’ah rules in a manner the mujtahid feels unable to exert any more.

Ijtihād has been proven by the text of the hadīth. It has been narrated about the Prophet  that he said to Abu Musa  when he sent him to Yemen:

And it has been narrated about him  that he said to Mu’az and Abu Musa al-Ash’ari having dispatched them to Yemen:

This Analogy (qiyas) is Ijtihād by deriving the hukm and the Prophet  accepted it from them. It has been reported about him  that he said to Mu’az when he sent as Wali (governor) to Yemen:

This is clear in the Prophet’s  acceptance of Mu’az’s intention to practise Ijtihād and there is no one who disputes the legality of Ijtihād. Furthermore, an ijma’ (consensus) of the Sahabah  took place on the issue of judging by an opinion which has been deduced from the Sharī’ah evidence i.e, they have agreed on the use of Ijtihād on any incident that takes place for which no (clear) text has been found. And this is what has reached us in successive reports (tawatur) in which there is no doubt. One such report is the saying of Abu Bakr  when he was asked about the Kalala. He said: ‘I will speak about it according to my opinion. If it is correct then it is from Allah . If it is a mistake then it is from me and from Shaytan and Allah  has nothing to do with it. Kalala is the one who has no children or parents left.’ His statement: ‘I will speak about it according to my opinion’ does not mean this opinion is from him. Rather it means I will say according to what I understand from the expression ‘Kalala’ in the verse. Kalala in the Arabic language applies to three people; the one who did not leave a child or parent or the one who does not have a son or a father from his descendants and the relatives from other than the direction of the child or father. So which of these meanings would apply to the word kalala in the verse ? Abu Bakr  understood it to have one of those meanings in His  saying:

Kalala is the predicate (khabar) of the verb ‘to be’ (kana) i.e, if the man leaves no ascendents or descendents to inherit after him. He  probably understood this also from the second verse:

And also from the hadīth which has been reported about the cause of the verse:

It has been reported that the Messenger  visited Jabir ibn ‘Abd Allah  who was ill. He said: I leave no ascendents or descendants. What shall I do with my wealth? Thus the verse:

was revealed in response to the question of Jabir. This opinion which Abu Bakr  stated is an Ijtihād and it does not emanate from himself. Also from this Ijtihād Abu Bakr  included the mothers mother in the inheritance to the exclusion of the father’s mother. Some of the Ansar said to him:

So Abu Bakr  gave both grandmothers equal shares in the inheritance. Abu Bakr  also used to give equal gifts to the Muslims. ‘Umar  said to him concerning this matter:

Abu Bakr  answered:

Likewise ‘Umar  said:

n the time of ‘Umars  rule a woman passed away leaving behind a husband, mother, two maternal brothers and two paternal fathers. ‘Umar first thought that the maternal brothers should have the third as their right, but this left nothing to the paternal brothers. The paternal brothers approached ‘Umar  and said to him:

So ‘Umar  changed his mind and gave all the brothers equal shares in the third, in spite of the fact the Sahabah had judged differently. They had given the husband one half of the inheritance, one sixth of the inheritance was given to the mother as decreed in the text, and the final third was given to the maternal brothers as also determined in the text, thus leaving nothing for the paternal brothers. ‘Umar  understood that the maternal brothers were brothers of the man from his mother’s side, but this applied not just to the maternal brothers but also to the paternal brothers. The mother was the common factor between them all, so when nothing had been left to the paternal brothers, their right was of what they deserved from the maternal brothers. The rest of the Sahabah saw it differently; they understood the text and made their own Ijtihād. Consider also the case when a Muslim, named Samrah took from a Jewish merchant a tenth portion of alcohol (as customs), bottled it and then sold it. So ‘Umar  said

In this case, ‘Umar  made the analogy between the alcohol and the fat, and that prohibition of it meant prohibition of its selling price. A further example of Ijtihād is what ‘Ali  said regarding punishment (Hadd) for the crime of drinking alcohol. He said:

Like ‘Umar  in the previous example, ‘Ali  made an analogy between drinking and fabrication of lies because he understood from Shar’a that which is likely to happen is treated the same as that which happens. This is like when the Shar’a treated sleeping the same as ritual impurity, and the act of sexual intercourse in requiring the Iddah (legal period a woman waits after divorce for marriage) the same as if the womb had become engaged (pregnant). All these are examples of Ijtihād by the Sahabah and Ijma’a as-Sahaba on the issue of Ijtihād.

The application of a hukm on issues which are classified under it is not considered Ijtihād rather but only as the comprehension of the Sharī’ah rule. Since Ijtihād is the inference of a hukm from the text whether from its wording (mantooq), understanding (mafhoom), from its indication (dalalah)

or from the ‘illah which has been mentioned in the text. Whether the inference was an inference of a comprehensive hukm (hukm kulli) from a comprehensive evidence (dalīl kulli); for example, the inference that a punishment should be imposed on the thief since the legislator made the cutting of the hand a hadd punishment for theft. Or the inference could be of a partial hukm (hukm juz’i) from a partial evidence (dalīl juz’i); such as the deduction of the hukm of hiring since the Prophet PBUH

Or like the inference of the hukm of giving the worker his wage after he has finished his work due to the Prophet’s  saying:

It is a partial evidence for a partial hukm. So this inference of a comprehensive hukm from a comprehensive evidence and the inference of a partial hukm from a partial evidence, all of this is considered Ijtihād because it is the adoption of a hukm from a dalīl whether the hukm was general which was extracted from a general evidence or the hukm was specific which was extracted from a specific evidence. All of it constitutes exerting one’s outmost in understanding the hukm from the evidence. As for the application of the hukm on new issues which fall within its meaning or is classified under it being one of its constituents, this is not regarded as Ijtihād. For example, Allah  has forbidden carrion. When a cow is killed by striking a blow to its head until it dies, its meat is not eaten because it has died as carrion and it was not lawfully slaughtered and the flesh of carrion is harām. And the hukm of tinned meat, which comes from the cow which has not been slaughtered lawfully, eating and selling it is harām in the Sharī’ah. This hukm has not been deduced; rather it is classified under the word ‘carrion’. For example, the animals slaughtered by the Druze are not eaten because it has not been slaughtered by Muslim or someone from the people of the book. So this hukm, i.e, the prohibition of eating the slaughtered animal of the Druze, has not been deduced. Rather a hukm which is already known has been applied on it, which is the prohibition of eating the animals slaughtered by the disbelievers who are not from the people of the Book. For instance, the permissibility of a woman being a member of the majlis al-Shura is a Sharī’ah rule. This hukm has not been deduced; rather the hukm of Wikala (representation) has been applied to it. The membership of the majlis al-shura is the representation of an opinion. It is allowed for the woman to delegate others to put forward opinions and she can represent others in their opinion. For example, Zakat is not given to anyone other than the one who is poor and his poverty is ascertained by speculative indications for which evidence has been furnished for its lawful consideration. Judgement is not passed without the statement of a just person (‘adl) and his trustworthiness (‘adala) is known by (the least amount of) doubt. And similarly, someone making inquiries to find out the qibla (direction of prayer) until the qibla is known after the investigation and others such examples. All these matters are not arrived at by way of Ijtihād which is the inference of rules from the Sharī’ah evidences but by way of applying the rules on the detailed issues (juz’iyyat) or by understanding the detailed issues and applying the rulings on them. This practise falls under the scope of the judiciary (qadā’) and does not come under Ijtihād. This practise is not considered Ijtihād because it does not determine a specific Sharī’ah rule but only applies a Sharī’ah rule on an incident which has already been decided and understood, when another incident of a similar type happens, the rule is applied on it similar to the initial incident and so it is not considered Ijtihād. The Sharī’ah rules require application after understanding them from the evidence and not Ijtihād, which is contrary to the Sharī’ah texts which require Ijtihād in order to adopt the hukm Shari’. Therefore,

The texts of the Islamic Sharī’ah require the Muslims to perform Ijtihād. This is because the Sharī’ah texts have not come in a detailed manner but have come in ambivalent form (mujmal), applicable to all incidents involving the human kind. Understanding them and deducing the hukm of Allah  from them requires the expending of effort to adopt the hukm Shar’i for each incident. Even the texts which have come in an elaborate manner and deal with details, they are in fact general (‘amm) and ambivalent (mujmal). For example, the verses of inheritance have come in an elucidatory manner and deal with minute details, despite that in terms of the partial rules they still require comprehension and deduction in many issues such as the issue of kalala and issues of disinheritance (hajab). All the Mujtahideen take the view that the male or female child take precedence in inheritance over the brothers of deceased because the word ‘walad’ (child) refers to children of both sexes. Ibn 'Abbas holds the view that the girl does not have such role because the word 'Walad' refers to a male only. This shows that even the texts which treat various issues in detail have come as ambivalent (mujmal), and that understanding and deducing a hukm from them requires Ijtihād. However, these texts which deal with details require application to newly occurring incidents. This application however is not what is meant by Ijtihād. What is intended is the inference of a hukm from its ambivalent/equivocal (mujmaliha) even if they deal with details, they are general (‘amm) and ambivalent/equivocal (mujmal) and they are the legislative texts. It is the nature of legislative texts to be general and ambivalent/equivocal (mujmal) even if they dwelve on details. The Sharī’ah texts, whether they are from the Qur’ān or from the Sunnah are ; the best legislative texts for the field of thought, the widest of scope for generalisation, and the most fertile ground to cultivate general principles. And they alone are suitable as legislative texts for all peoples and nations. As for being the best texts for the field of thought that is observable from the way in which they encompass all types of relationships. This is because relationships of all types, whether relationships between individuals or relationships between the state and citizens or relationships between states, peoples and nations. However new and multifarious these relationships may be, the thought is able to deduce rulings for them from those Sharī’ah texts, Therefore they are the best texts for the field of thought from all the legislative texts. As for it having the best scope for generalisation, that is clear from its sentences, words, style of formulating (expressions) in terms of its encompassment of the wording (mantuq), understanding (mafhum), meaning (dalāla) and justification (ta’leel) and analogy to the ‘illah which makes the inference for every action feasible, permanent and inclusive. This insures that it is able to encompass everything, being complete and general. As for it being the the most fertile ground to cultivate general principles, that is apparent from the abundance of general meanings which these texts contain and from the nature of the general meanings. That is because the Qur’ān and the hadīth have come along broad lines even when touching on details. The nature of these broad lines is that they give the Kitab and Sunnah general meanings under which general and specific issues can be classified. And it is from this the abundance of general meanings come. In addition, these general meanings contain real and perceptible issues and not hypothetical issues that have been arrived at theoretically or logically. And at the same time they are there to solve the problems of man and not only for specific individuals that is, to clarify the ruling for the action of human beings, whatever be the instinctual manifestation that may have pushed them to this action. That is why they are applicable to diverse meanings and many rulings. Thus, the Sharī’ah texts are the most fertile ground for producing the general principles (qawaid ‘Aammah).

The Sahabah formed an ijma’ (consensus) that the sin is taken off from the Mujtahiddin in the Sharī’ah rules in terms of the speculative fiqhi (jurisprudential) issues. As for the definite issues such as the obligation of the worships, prohibition of fornication and murder there is no Ijtihād or dispute with respect to them. That is why the Sahabah  disagreed on the speculative issues and not on the definite issues.

The mujtahid in the speculative issues is correct in what he has arrived at by his Ijtihād even if he is liable to make a mistake in his opinion. However, being correct does not mean that he has hit the true target because this does not agree with the reality of a speculative rule since the Messenger  called him a mukhti’ (one who has made a mistake). Rather what is meant by saying that the mujtahid is right is in terms that do not rule out a mistake and not in terms of hitting the true target (isaba) which is the opposite of mistake. So describing someone who makes a mistake in Ijtihād as right (musib) is in the meaning that the text rewards the mujtahid even when he makes a mistake and not in the sense that he did not make a mistake. Therefore, every mujtahid is right according to what he thinks is right which does not rule out mistake. It is in terms of getting it right and not in terms of hitting the true target.