Sheikh Salman al-Oadah
In the narration of a hadîth, some narrators are known to have been guilty of trying – without lying – to improve the appearance of the hadîth’s chain of transmission. This is referred to in the field of hadîth criticism as tadlîs. Scholars of hadîth criticism identify three basic kinds of tadlîs:
1. Tadlîs al-tajwîd (making good): This is where a later narrator of a hadîth fails to mention the name of a weak narrator who comes between two reliable narrators.
This is done in cases where the two reliable narrators are contemporaries of each other. A later narrator – the one who is guilty of tadlîs – fails to mention the weak narrator that comes between the two reliable narrators. He achieves this by using language that does not imply that the two strong narrators actually heard the hadîth directly from each other. The word `an is often used between the two reliable narrators, which simply means “he quoted…” without implicating that the first reliable narrator heard the hadîth directly from the other. In this way, mention of the weak narrator is avoided.
This is the worst kind of tadlîs. It is so serious that some classical hadîth critics were of the view that a person known to be guilty of it should be rejected as a narrator and that all his narrations should be rejected. Other critics, however, accept the hadîth of such narrators, but only in cases where they use language which explicitly states that all the people in the chain of transmission heard the hadîth directly from each other.
2. Tadlîs al-shuyûkh (obscuring the source): This is where the narrator refers to his sheikh – the person from whom he heard the hadîth – by a name or title other than the one the sheikh is commonly known by.
3. Tadlîs al-isnâd (obscuring the quote): This is where the narrator quotes from someone something that he had heard from him indirectly, but uses ambiguous language (like `an) to obscure the fact that he actually heard it indirectly. He might simply say things like: “So and so said…”
Source: Islam Today