Abu Ja'far al-Baqir (676-743 AD) 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 AD) established a genealogical link between Ishmael and Muhammad using writings 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' (of his time) were 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 Muslims.[d] According to author and scholar Irfan Shahîd, while Western scholars viewed this kind of genealogical Ishmaelism with suspicion, the concept can be supported, Genealogical Ishmaelism was viewed with suspicion 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 short 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 Muhammad 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 Ishmaelite tribes.