According to the fifth category, a hadeeth can also be classified with respect to the nature of its text and isnad.  According to Al-Shafi’i, if a hadeeth reported by a trustworthy person goes against the narration of someone more reliable than him, then the hadeeth is shadh or “irregular”.  According to Ibn Hajar, if a narration by a weak reporter contradicts an authentic hadeeth, then that hadeeth is classified as munkar (“denounced”), although some scholars would classify any hadeeth of a weak reporter as munkar.  A hadeeth could also be classified as munkar if its text contradicts general sayings of the Prophet.  If a hadeeth reported by a reliable person contains some additional information not narrated by other authentic sources, the addition is accepted so long as it doesn’t contradict them, and the addition is known as ziyadatu thiqah (“an addition by one trustworthy”).  However, if a reporter adds something to the hadeeth being narrated, then the hadeeth is classified as mudraj or “interpolated”.  If this occurs in a hadeeth, then it is usually in its text and often for the purpose of explaining a difficult word.  In a few examples this occurs in the isnad - a reporter takes a part of one isnad and adds it to another isnad.  A reporter found in the habit of intentional idraj or interpolation is generally considered a liar, although scholars are more lenient with those reporters who may do it to explain a difficult word (Hasan 37-39).

In the sixth category, hadeeth that contain hidden defects in their isnad or text are classified as ma’lool or mu’allal (“defective”).  This could be due to such things as classifying a hadeeth as musnad when it is actually mursal or attributing a hadeeth to a particular Companion when it really comes from another one.  In order to detect such defects, all the isnads of a hadeeth have to be collected and examined.  For example,

“Some scholars wrote works on which Successors heard hadeeth from which Companions.  From this information is it known that Al-Hasan Al-Basri did not meet Ali, although there is a slight chance that he may have seen him during his childhood in Madinah.  This is significant as many Sufi traditions are said to go back to Al-Hasan Al-Basri who is said to have reported directly from Ali.” (Hasan 42-43)

There can also be uncertainty about the isnad or text, in which case the hadeeth is classified as mudtarib (“shaky”).  This occurs if reporters disagree about some points in the isnad or text in such a way that no opinion prevails.  A hadeeth may be classified as maqloob (“changed” or “reversed”) if in the isnad a name was reversed (i.e., Ka’b b. Murra versus Murra b. Ka’b) or if the order of a sentence in the text is reversed (Azami 66).  This also applies to those hadeeth whose text has been given a different isnad or vice versa, or those in which a reporter’s name was replaced with another (Hasan 41-42).

The seventh and last category to be discussed here is classification according to the quality of the reporters, upon which the final verdict on a hadeeth critically depends.  Hadeeth reported by those known to be adil, hafiz, thabit, and thiqa are the highest ranked hadeeth and are classified as saheeh or “sound.”  For someone to be considered adil, he had to be a very pious Muslim, honest and truthful in all of his dealings.  Through careful comparison, verbal agreement found in the text of a hadeeth among various transmitters indicated who was the most accurate (thabit), the most reliable (thiqa), and who had the best memory (hafiz).  If any scholar falls less than this ideal in one or more categories, but he is not criticized, then the hadeeth reported by him are judged to be less sound, or hasan (“fair”).  If a reporter was known to have a weak memory or make mistakes due to carelessness, then his hadeeth are judged as da’eef (“weak”) (Burton 110-111).

Of course, there are other factors which play into the final verdict on a hadeeth, and in the words of Ibn Al-Salah, “A saheeh hadeeth is the one which has a continuous isnad, made up of reporters of trustworthy memory from similar authorities, and which is found to be free from any irregularities (i.e. in the text) or defects (i.e., in the isnad).”  According to Al-Tirmidhi a hasan hadeeth is “A hadeeth which is not shadhdh, nor contains a disparaged reporter in its isnad, and which is reported through more than one route of narration” (Hasan 44-46).  A hadeeth that doesn’t reach the requirements for a hasan hadeeth is classified as da’eef, and often this is due to discontinuity in the isnad.  It can also be classified as da’eef if one of the reporters does not have a good reputation for whatever reason, be it because of his making many mistakes or being dishonest.  If the defects are many and severe, then the hadeeth is closer to being classified as mawdu’ or fabricated.  According to Al-Dhahabi the mawdu’ hadeeth is the one whose text goes against established norms of the Prophet’s sayings or whose isnad contains a liar.  A hadeeth can also be established as mawdu’ due to “external evidence related to a discrepancy found in the dates or times of a particular incident” (Hasan 49).

In conclusion, the aforementioned classifications constitute only a fraction of the total number of classifications that exist.  The studies in hadeeth are very complex, and it seems that the scholars thought of every imaginable angle from which to analyze hadeeth.  All this was for the purpose of distinguishing between different types of narrations, especially for distinguishing the authentic from the inauthentic.