One of the most important rules of Islamic jurisprudents, which have vital significance in Islamic jurisprudence, is Istishab. ". It has been used as a solution of various social, personal and economic proЫems after the time of Holy prophet (s.a.w) and his pious Caliphs. It is practiced and counted up as a rule of Sharia after the HoIy Quran and Sunnah as a solution for most of the probems. "Istishab" means presumption of continuity or the continuance of companionship. Technically it refers to the presumption of constant of an earlier rule or continuance absence. In this sense it is used for the maintenance of a status with respect to the ru1e. The previous rule is accepted, unless a new rule is found that goes against. It is an easy orientation one may refer to "lstishab" as the "accompanying rule. But the fact is that, Istishab is neither a source of law nor it is a source for estaЫishing new rules, but it is mereIy a set of presumptions. Istishab is practiced and used as a rule till the time a new rule is estaЫished which is derived from the HoIy Quran and Sunnah as a Hukm. "Shakk" is an important part of human Iife and Istishab has solution for this problem of "Shakk" therefore Istishab is used as one of the sources of sharia after HoIy Quran, Sunnah, Ijma, Qiyas and personal activity of human life. Moreover, І tried to discuss Istishab in the light of the Ah1-e-sunnat аr1d Ah1-e-tashayyo researchers of Usol-e-Fiqah which is the need of this time for the unity of Muslim Ummah. So 1 suggest to alI researchers specially the researchers of Islamic studies to comprise the aII Muslims ideas with broad mind, so our struggles may become a source to bring Muslim Ummah closer to each other and give a message of unity, реасе and harmony. The thesis deals with its main four chapters and their sub-chapters: Frist Chapter is containing complete definition of lstishab in the light of scholars of both sects and compression between the views of them. Second Chapter contains the Arguments of scholars from both sects on the Hujiayat- e-lstishab (acceptance) in the light of HoIy Quran, Sunnah, Ijma, and AqI and contrast between them. Third chapter is containing arguments of the Munkeren-e-Istishab (one who rejects Istishab) from the scholars of both sects and contrast the views from both of them on the acceptance and rejection of Istishab. Last chapter is focusing on an overall view of Istishab from the HoIy Quran, Sunnah and Aql, some important topics of Istishab and the views of scholars on it. At the end the thesis leads to its consequence that lstishab is an accepted rule of Islamic jurisprudence in all Islamic sects in the Iight of НоІу Quran, Sunnah, Ijma and Aqal, but the lstishab is neither designated as a permanent rule nor designated a source for estaЫishing new rules. Hopefully, this kind of research can provide a base to bring peace and harmony among the various segments of the society.