Twelfth: tadlīs (concealment), which is of two kinds.

First: tadlīs of the isnād. This occurs when a narrator relates from a contemporary something he never actually heard from him, yet gives the impression that he did so by saying, “So-and-so said …,” or “from so-and-so …,” and the like. At times he may retain his own teacher in the chain but omit another transmitter—someone weak or very young—in order to make the ḥadīth appear more sound.

Second: tadlīs of the shuyūkh, in which the narrator refers to his teacher by an unfamiliar name, kunya, lineage, or description.

Regarding the first kind, it is gravely disliked; most scholars have censured it. Some went further, holding that anyone known for it becomes impugned and his narrations are rejected, even if he later clarifies having heard them. The correct view is more nuanced: whatever he transmits with wording that leaves the question of direct hearing ambiguous is treated as mursal, whereas anything he conveys with explicit expressions such as “I heard,” “he narrated to us,” or “he informed us” is accepted and relied upon. Many examples of this appear in the two Ṣaḥīḥs and elsewhere, narrated by Qatādah, the two Sufyāns, and others. The same ruling applies even to one who has practiced tadlīs only once. Any report found in al-Bukhārī, Muslim, or similar works that comes from a mudallis using the term ʿan (“from”) is presumed to rest on proven audition from another route.

As for the second kind, its reprehensibility is lighter, the objection being merely that it makes the teacher harder to identify. The level of censure depends on the narrator’s motive: disguising someone weak, very young, or late-died, or wishing to avoid constant repetition when he has heard a large number of ḥadīths from that teacher. Al-Khaṭīb and others have shown leniency in this matter. Allah knows best.