The omission may be from the end of the isnād, after the tābiʿī, this is al-mursal.1
Examples from Shaykh Muḥammad Abū Shuhba's al-Wasīṭ fī ʿUlūm wa-Muṣṭalaḥ al-Ḥadīth (ʿĀlam al-Maʿrifa edition). Of al-mursal: Imām Mālik narrated from Zayd ibn Aslam, from ʿAṭāʾ ibn Yasār, that the Messenger of Allāh ﷺ said: "The severity of the heat is from the raging of Hell, so when the heat grows severe, delay the prayer until it cools." ʿAṭāʾ is a tābiʿī, so the Companion has dropped from the end of the chain (p. 281). Of al-muʿḍal: Mālik says in the Muwaṭṭaʾ, "It has reached me from Abū Hurayra," that the Messenger of Allāh ﷺ said: "The owned slave is entitled to his food and his clothing in the customary way, and he is not to be charged with work beyond his capacity." Mālik himself narrates this ḥadīth with a connected chain outside the Muwaṭṭaʾ, from Muḥammad ibn ʿAjlān, from his father, from Abū Hurayra, from which it is known that two narrators have fallen out together (pp. 290 to 291). [tr.] ↩
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.
An omission of two or more consecutive narrators at any point in the chain is al-muʿḍal, one of the four kinds of rejected report rooted in a break in the chain.
The rejected report falls into two kinds: that rejected because of an omission in the isnād, and that rejected because of criticism of the narrator.
Al-Shāfiʿī accepts the mursal under three conditions; some Shāfiʿīs treat the third as one of the four corroborating supports, leaving two conditions.
