Some historiographical preference for prose sources over poetic ones is justifiable. The narrative content of Classical Arabic poetry is largely determined by occasion and convention, and its formal constraints clash with the “unvarnished” texture of veridical discourse. Conversely, prose’s mimetic nearness to unrhymed speech (the default vehicle for eyewitness testimony) lends it a certain epistemic privilege. Prose too is artifice, though, and for the purposes of simulating, enhancing and otherwise representing real-life experience it is notoriously apt. Its historiographical value relative to poetry’s is therefore an open question, and for raising it one useful figure is Ka‘b b. Mālik (d. ca. 50/670). A Medinan companion of Muḥammad, Ka‘b not only commemorated the Prophet’s military affairs through the medium of poetry, but was a much-quoted source of prose ḥadīth of the post-Emigration period (beginning with the second oath of ‘Aqaba, for which he was present). Ka‘b’s unrhymed narrations include a long, emotional report of a fifty-day period of ostracism he underwent at Medīna, consequent upon his abstention from the campaign of Tabūk in the summer of 9/630. Throughout the iterations of Ka‘b’s report in ḥadīth, sīra and tafsīr (with reference to Sūrat al-Tawba 9:117-8), the stability of its wording points to a common source in the written notes of Ibn Shihāb al-Zuhrī (d. 124/742), who took it down from Ka‘b’s grandson. Ibn Shihāb is known to have made his notebooks available to his students, including Muḥammad ibn Isḥāq (d. 150/767), author of our earliest extant source for Ka‘b’s ordeal. This paper’s correlation of Ka‘b’s report with the poems of his dīwān (in addition to his other unrhymed contributions to ḥadīth and sīra) is one paradigm for a recorrelation of commemorative poetry and discursive narration in prose – mimetic vehicles whose formal differentia co-align variously with relative historiographical value.