The Islamic Personality by Sheikh Taqīuddīn An-Nabahānī

It becomes clear from dividing the hadīth into Sahih, hasan and da'eef that the hadīth hasan and Sahih are both advanced as proof and the da'eef hadīth is not. What makes the hadīth acceptable or rejectable is the consideration of the sanad, transmitter and matn. If a narrator is not ommited from the sanad whose ommision will lead to the inibility to attest the reliablity of the ommitted narrator and the narrator's probity is not impunged and the matn is not weak and does not contradict any part of the Qur’ān or the mutawatir Sunnah or definite ijma', then in this case the hadīth is accepted, acted upon and adopted as a Sharī’ah evidence whether it was Sahih or hasan. As for when the hadīth is contrary to these qualifications it is rejected and not educed as proof. Therefore, the rejected hadīth is the hadīth which is rejected due to the ommision of a narrator from the sanad which results in the inability to attest the reliabilty of this narrator or due to a narrator's probity being impungned, or due to the weakness of the (matn) of the hadīth or its contradiction with the Qur’ān, hadīth and ijma' which are definite. Various types of hadīth come under the hadīth mardud (rejected), following are their characteristics:

1. Mu'allaq: when there is one or more narrators consecutively missing from the beginning of the sanad in a manner that is quite obvious. The term 'more' is more general to include the whole or part of the isnād. Also included is the ommision of the whole chain by the muhaddith or the hadīth compiler, such as when he says: The Messneger of Allah  said or did such and such thing.

2. Mu'dal: Is a chain in which two or more narrators are missing from one or more places. It includes when the tabi at-tabi'i omits a tabi'i and sahābi from the isnād. It does not include the statement of authors from the fuqaha when they say:

Or their statement

It is not mu'dal becaue it is not a transmission, rather it constitues qouting and educing a proof which is correct.

3. Munqati': When a single narrator is missing before the Sahābi from one of the places. If there is more than one place such that the narrator who ommits does not ommit more than one narrator from each place then it will be munqati' in these places. Also considered to be munqati' is the chain in which there is a obscure narrator (mubham). An example of a transmitter being ommitted is what has been narrated by 'Abd al-Razzaq from al-Thawri from Abu Ishaq from Zayd ibn Yathi' from Hudhayfa, which goes back to the Prophet  that he said:

The isnad has breaks in two places. Firstly, 'Abd al-Razzaq did not hear from al-Thawri but rather narrated it from al-Nu'man Ibn Abi Shayba al-Jundi who narrated from al-Thawri and secondly, al-Thawri did not hear from Abu Ishaq but rather narrated it from Shurayk who narrated from Abu Ishaq. The hadīth, therefore, is rejected. An example of a transmitter being nondescript is what is narrated by Abu al-'Ala ibn 'Abd Allah ibn Shukhayr from two men from Shaddad ibn Aws:

Therfore, the hadīth is rejected due to the presence of unknown (majhul) narrators in the transmision.

4. Shadh: It is when a reliable transmitter narrates a hadīth which condradicts what others have narrated. It is not shadh if a reliable narrator transmits something no one else has narrated. Because the narration of a reliable transmitter is accepted even if others have not narrated it and it is used as a proof. It is like the hadīth:

Only 'Umar narrated it and from him only 'Alqama narrated it. A single narrator Muhammad ibn Ibrahim al-Tamimi narrated from him from who only Yahya ibn Said al-Ansari narrated. From Yahya ibn Said there was a proliferation of transmission routes. Therefore, the shadh is only when a reliable narrator transmits somthing which contradicts what has been narrated by others i.e, when the accepted narrator transmits a report which goes against the report of those more likely to be correct in their transmission.

5. Mu'allal: It is a hadīth which has a defect ('illah). It is the hadith which is discovered to have a defect which impairs its authenticity, although it apparently seems to be sound. It goes back to the isnād whose transmitters are reliable and which apparently includes the conditions of authenticy.

6. Munkar: What a single unreliable transmitter narrates alone. The munkar is the narration of a weak narrator which contradicts the report of a transmitter who is less weaker.

7. Mawdu': The hadīth mawdu' is the forged and fabricated hadīth. The fabricated hadīth is the evil of the weak ahadīth. The narration of anyone whose condition is known is not allowed except when it is linked to clarifying its fabricated status. A hadīth is known to be fabricated when the forger acknowledges its fabrication or something which is tantamount to the position of a confession. The fabrication can be understood from the indication of the transmitter's condition, such as the narrator following the whims of certain leaders in his lies or while he is attributing the hadīth he is caught as a consummate liar because that report does not come from any route other than him, no one agrees with him and he has no witness or we can discern mendacity from the condition of what has been narrated i.e, from the state of the matn, if it is weak in its wording or meaning or it contradicts some of the Qur’ān, mutawatir sunnah and definite ijma'. There are diffent types of hadīth fabricators. The ones causing most harm are those associated with zuhd (pious ascetism). They fabricated hoping to get reward for what they alleged. The danger is that people accepted their fabrications, trusting and relying on them. Then when a forger fabricated a saying the people narrated it. Probably, he took a saying from the sages or others and falsely ascribed it to the Messenger of Allah . From the fabricated ahadīth are the ahadīth about the excellence of the Qur’ān Sura by Sura especially narrations (allegedly) on the authority of 'Ubay ibn Ka'ab and the isnād: Abu 'Isma > 'Ikrama > Ibn 'Abbas. Its spuriousness has been established from the study (cross refrences) of scholars and by the confession of Abu 'Isma. It has been narrated that he said:

These are a selection of the types of rejected ahadīth but they are not all the possible types that could be mentioned. There are many types of rejected ahadīth for which mentioning a part is suffient as a principle by which the acceptable and rejected hadīth is known. A hadīth is not rejected because it does not meet the conditions for the catagory of Sahih as long as its sanad, transmitters and matn are acceptable i.e, when it is hasan since the narrators are of lesser reliability than the narrators of the Sahih hadīth or if there was a mustur (a transmitter whose record is apparently blameless) or he had a bad memory or it has been strengthend by a qarina (indication) or its acceptance is prepodentarent such as when it is strengthend by another narrator agreeing with it or there is a witness i.e by a narrator who is assumed to be isolated or by another Hadith. One should not be overstrict in rejecting a hadīth as long as it is possible to accept it according to the requirements of the sanad, tarnsmitters and matn. Especially when the majority of the ‘Ulamā have accepted it and the fuqaha have generally used it, then it is worthy to be accepted even if it did not meet the conditions of the Sahih because it comes under the hasan. Just as one should not be overstrict in rejecting a hadīth at the same time it is not allowed to be negligent with respect to the hadīth, accepting the hadīth which is rejected due to the sanad, transmitter or matn.