An omission from the isnād, if it is made with the intention of suggesting that one heard from a transmitter from whom one did not, is al-mudallas; otherwise it is al-mursal.1
The omission in al-mursal may be concealed, in which case it is al-mursal al-khafī; or it may be evident, in which case it is al-mursal al-wāḍiḥ. Concealment and clarity here are relative, varying with the rank of the critic.2
Ḥāfiẓ Ibn Ḥajar confines tadlīs to one narrating from a shaykh he is known to have met, assigns the mere contemporary to al-mursal al-khafī, and insists that the two be kept apart (Sharḥ Nukhbat al-Fikr, p. 424). Muftī Muḥammad ʿAbd al-Mālik al-Kumillāʾī answers him under the heading "The difference between concealed irsāl and tadlīs" (al-Wajīz fī shayʾ min muṣṭalaḥ al-ḥadīth al-sharīf, pp. 230 to 232, where Ibn Ḥajar's words are quoted at p. 232). The imāms, he replies, did use tadlīs where there was a meeting without established hearing, and what they attended to in calling something tadlīs was deception, or at least the suggestion that nothing was omitted, whereas their use of irsāl was wider than that (p. 230). They used irsāl both of omissions plain to anyone who knows the ṭabaqāt and of omissions only the expert critics of ʿilal detect, the later scholars naming the second sort al-mursal al-khafī (p. 231). Two of his instances: Imām Muslim, in the muqaddima of his Ṣaḥīḥ, says "arsala" of imāms who dropped an intermediary between themselves and a shaykh they had met and heard from, but not heard that ḥadīth from; and the reports the Companions and mukhaḍramūn did not take from the Prophet directly are called marāsīl, never mudallasāt (p. 230). [tr.] ↩
Inferred from al-Khaṭīb's al-Kifāya (p. 476) and elsewhere, and Uṣūl al-Jaṣṣāṣ, 2/61 to 62. I (the author) say: ʿAllāmah al-ʿIrāqī supposed that the basis of the distinction between irsāl and tadlīs is contemporaneity (or its absence); his statements on the matter were therefore inconsistent, and his position is contradicted by the irsāl of the mukhaḍramīn, which is not called tadlīs. Al-Ḥāfiẓ supposed that the basis is the meeting itself (or its absence); this position, and al-ʿIrāqī's all the more so, is contradicted by the irsāl of the ṣaḥābah and by Imām al-Bukhārī's irsāl from his teachers, since al-Bukhārī was the furthest of Allāh's creation from tadlīs, as ʿAllāmah Ibn al-Qayyim said. The correct view is that contemporaneity and meeting are necessary preconditions for the suggestion of audition, since one cannot intend to suggest audition without contemporaneity, but the basis of the distinction is not these themselves. The basis is rather the suggestion itself, and there is no necessary connection between it and them, since a man may narrate as mursal from one whom he did meet, while making clear that he did not hear it from him, as when he narrates with the wording "I was told about so-and-so", "it reached me from so-and-so", "a man narrated to me", and the like. But because these formulations were not counted among the marāsīl by the later scholars, it did not occur to al-ʿIrāqī or to Ḥāfiẓ Ibn Ḥajar that the connection is not a necessary one. Reflect on this; and Allāh knows best. See: al-Taqyīd wa-l-Īḍāḥ, pp. 32 and 81; Nukat Ibn Ḥajar, the discussion of tadlīs; Ighāthat al-Lahfān, 1/260. ↩
Al-mursal al-khafī is a mursal whose omission is concealed; clarity and concealment are relative, varying with the rank of the critic.
Al-mursal al-wāḍiḥ is a mursal whose omission is evident; clarity and concealment are relative, varying with the rank of the critic.
Al-mursal is an omission from the end of the isnād, after the tābiʿī; one of the four kinds of rejected report rooted in a break in the chain.
An omission from the start of the isnād by the compiler's action is al-muʿallaq, one of the four kinds of rejected report rooted in a break in the chain.