Abstract
Yemen is in the southern region of the Arabian peninsula. al-Hadi ila-1-Haqq Yahya b. al-Husayn [245-298/859-911], the first Imam al-Zaydi al-Shii in Yemen, arrived at Sa^cda and Najran which are cities in Northern Yemen by the request of the tribes in those cities. They invited him as a mediator for settling their deep disputes since the time of Jahiriya. In the former researches about the arrival of al-Hadi at Yemen, most of the results are only a description of what followed his activity chronologically. But I have a question about that, namely, why he was invited as a mediator? I think that if the tribes wanted someone to mediate in their desputes, a person with the ability to mediate was available. They did not need to call him for it. In this research, I have examined the arrival of al-Hadi at Yemen by investigating his biography both in the tribal aspect and the al-Hadi's aspect. In the conclusion I have pointed out that the tribes in Yemen have some consciousness of the worship of the Prophet and his descendants, so they invited al-Hadi who is a descendant of the Prophet.
