The majority of Sayyid believe they are one of the modern day descendants of Prophet Muhammad, and that they are therefore the descendants of Prophet Ishmael and his second son Prophet Qedar. Imam Abu Ja'far al-Baqir (676-743 CE) wrote that his father Ali ibn Husayn informed him that Prophet Muhammad had said: The first whose tongue spoke in clear Arabic was Ishmael, when he was fourteen years old. Hisham Ibn Muhammad al-Kalbi (737-819 CE) established a genealogical link between Prophet Ishmael and Prophet Muhammad using writings that drew on biblical and Palmyran sources, and the ancient oral traditions of the Arabs. His book, Jamharat al-Nasab (The Abundance of Kinship), seems to posit that the people known as Arabs are all descendants of Ishmael. Ibn Kathir (1301-1373) writes, All the Arabs of the Hijaz are descendants of Nebaioth and Qedar. Medieval Jewish sources also usually identified Qedar with Arabs and/or Muslims.[d] According to author and scholar Irfan Shahîd, Western scholars viewed this kind of genealogical Ishmaelism with suspicion, seeing it as, [...] a late Islamic fabrication because of the confusion in Islamic times which made it such a capacious term as to include the inhabitants of the south as well as the north of the Arabian Peninsula. But shorn of this extravagance, the concept is much more modest in its denotation, and in the sober sources it applies only to certain groups among the Arabs of pre-Islamic times. Some important statements to this effect were made by Prophet Muhammed when he identified some Arabs as Ishmaelites and others as not. Ishmaelism in this more limited definition holds that Ishmael was both an important religious figure and eponymous ancestor for some of the Arabs of western Arabia. Prominence is given in Arab genealogical accounts to the first two of Ishmael's twelve sons, Nebaioth (, Nabīt) and Qedar (, Qaydār), who are also prominently featured in the Genesis account. It is likely that they and their tribes lived in northwestern Arabia and were historically the most important of the twelve Ishamelite tribes.