We thank Allah, may He be exalted, after conducting this research under the title: "Two Biographies :Nasab al-Islām and Şifat al-Islāmby Wā'ilibnAyyūbal-Hadrami, a scholar of the second century AH, study and edition". These two manuscriptsconstitute some of the oldest traces of Ibadism, illustrating a number of their principles of belief, showing the features of jurisprudence, and giving the reader a general picture of this school of thought. The author of the two books is one of the leading Ibadi jurists. He has a number of fatwās in the Mudawwanahof AbūGhānim Al-Khurasānī. The research dealt with two main issues: the impact of the sins on faith in the Islamic schools, and the general rights of Muslims of other schools (Ahl al-Qibla) with regard to followers of Ibadism. It shows the following: That the Ibadischool emphasized the comprehensiveness of Imān of all orders and prohibitions, as the rootedness of this concept in the believer brings him to correct behavior and comportment, be it in his relation to his Creator or other human beings. That there is no difference between the terms Imān and Islām in their shar'ī connotation. The major sin is fixed by a peremptory text, therefore, the space for disagreement between the different Islamic sects is narrowed down. The general rights do not fall from the perpetrator of the sin, and his punishment is in the Hereafter, with the exception of disassociating from him unless he repents. The general rights of Ahl al-Qiblawith regards to followers of the Ibadi schoolare established. The sanctity of blood of Ahl al-Qibla, their wealth, and the prohibition to enslave their women. The right to pray behind them, the right to pray for them and to be buried in the graves of Muslims. The marriageto them, and inheritance among them. This is a summary of the research. It is a personal effort and it may be potentially right or wrong.