The main source of the jurisprudence of Zayd b. Ali, the founder of Zaydīyah School, is a book named al-Majmū‘ al-Kabīr. This book is ascribed to Zayd, but is compiled by his attendant and disciple, Abū Khālid Wāsiṭī. Zayd’s method was avoiding exaggeration and coordinating with the jurisprudence of the school of Medina, especially the jurisprudence of Ahl al-Bayt. al-Majmū‘ is consisted from three parts:
1- Traditions of the Prophet (S.A.W) narrated by Imam Ali (A.S.),
2- Traditions of Imam Ali (A.S.),
3- Zayd’s personal ijtihāds and elicitations, which are mostly in agreement with Sunni jurists,
Zayd’s writings are regarded as the main principles for Zaydīyah, from which derivative issues must be elicited.
Famous Zaydī scholars are as follows: Ḥasan b. Ṣāliḥ (d. 161 A.H.), Ḥasan b. Zayd b. Muhammad known as Imām al-Dā‘ī ilá al-Ḥaqq (who was ruling over Ṭabaristān from 250 to 270 A.H.), Qāsim b. Ibrāhīm ‘Alawī and his grandchild al-Hādī Yaḥyá.
1- Sources of Deduction
In conclusion, can assume that Zaydīyah rely on ten jurisprudential sources. However, not all these sources are within the same rank of reasoning. These ten deducing sources arranged in importance order, are as follows:
1- Absolute intellect: according to Zaydīyah, “absolute intellect” is the first source of knowledge. Because, resorting to the Qur’an and Sunnah is the next step after knowing God, and proving that the Qur’an is a Divine revelation to The Prophet. Then, proving these two subject matters is passible only by the means of “absolute intellect”. Therefore, it has priority over all other sources. Of course, it is different from “non-absolute intellect” that is useful for obtaining jurisprudential derivatives.
2- Absolute Ijmā‘ (consensus): it the second source in serial. Absolute ijmā‘ is the same as ḍarūrīyāt (necessary truths) of Islam, which means they the issues that have been unanimously accepted by all the Prophet’s Companions and all their Successors and the all generations after them until now. The issues such as five obligatory prayers in one day, or midday prayer contains four rak‘ats (a cycle of prayer).
3- The Qur’an and a Sunnah that is absolute and widely transmitted. In the viewpoint of Zaydīyah, the Qur’an and an absolute Sunnah are in the same rank; therefore, limiting and abrogating one by another is acceptable.
Note: the elicited concept from the Qur’an and Sunnah are presented in two ways:
· Nass: it is, in turn, of two kinds:
o Nass jalī (express statement), which means that the words originally bear no meaning except the elicited concept,
o Nass khafī (implied statement), which means that realizing that the elicited concept is the only meaning of that words needs to think and consideration,
· Ẓāhir (outer meaning): means that elicited concept is the preponderant meaning that makes haste to mind; however, there is a possibility of an inferior meaning, too.
According to Zaydīyah point of view, nass and ẓāhir are of the same grade. Therefore, ẓāhir is ignorable only in the case that there was a stronger nass against it; otherwise, they are within the same rank of credibility.
4- Single traditions: terms of resorting to a tradition with a single transmitter:
a. The transmitter must be righteous and reliable, and someone who is from the Prophet’s descendants is prior to others.
b. Narrated subject was not of generally involved matters; otherwise, it would be a mustafīḍ (diffused) tradition.
5- Concepts: a harmonious meaning is prior to a divergent meaning,
6- Uncertain ijmā‘ (consensus): there are different levels of ijmā‘ as mentioned bellow:
a. Absolute ijmā‘: that is the same as necessary truths of Islam, as was mentioned above.
b. The consensus of Companions after their extinct,
c. The consensus of Companions before their extinct,
d. The consensus of Companions on a matter after having disagreement about that,
e. The consensus of Successors after Companions’ disagreement,
f. Tacit consensus, meaning the consensus of mujtahids of an era, except one or two,
7- Words of ṣiḥābah: however all companions of the Prophet (S.A.W) are called as ṣiḥābah, but here it means Imam Ali, her eminence Fatimah, Imam Ḥasan, and Imam Ḥusein. Only their words are considered as a proof in the viewpoint of Zaydīyah,
8- Qiyās (judicial reasoning by analogy): Zaydīyah believe that however, qiyās only results in presumption, but it is a proof. Because, God has ordered to take it in some cases like determining qiblah and time. Zaydīyah regard istiḥsān (juristic preference) and maṣāliḥ mursalah (consideration of public interests of the time) as kinds of qiyās, just like Mālikīyah.
9- Istiṣḥāb (the principle of continuance): Zaydīyah do not regard istiṣḥāb as an independent proof, and divide it into four kinds:
a. The continuance of original exemption,
b. The continuance of landed property and ownership,
c. The continuance of ritual ablution for someone who was certain of his ablution and then has fallen into suspicion,
d. The continuance of disposition and attribute, like continuance of life for someone who has disappeared, to affirming the inheritance share for him,
10- Uncertain intellect: this source is applied in the case that there was no other source available. By meaning that, in the absence of any religious evidence, some scholars hold the principle of permissibility; some follow the principle of prohibition, and some of them practice the principle of continuance of original permissibility. However, intellect is the main scale for Zaydīyah in such cases, because it recognizes the good and badness of matters, and can judge about permissibility or prohibition, based upon having advantage or being harmful.