Takfeeri tradition in Islam is a tradition which is usually traced back to period of Imam Ibn Tammiyah (r.a) who declared newly converted Mongols as apostate because, even after converting to Islam, Mongols insisted on establishing Yasa Law instead of Islamic Shariah. In this way, a tradition was set in Islam through which fellow Muslim people, society or leaders might be declared as ‘kafir’, if practices of such Muslim people, society and leaders are found to be inconsistent or repugnant to what are considered to be Islamic ones. This ‘takfeeri’ tradition was carried forward in 18th century by Abdul Wahhab in Arab lands to fight against ‘sufis’ who were considered as practicing un-Islamic practices. The same ‘takfeeri’ tradition has been adopted practically by one section of Sunnis e.g. ISIS and al-Qaida, among others, and one section of Shiite community e.g. Iraqi Shiite community, among others. The hostility prevailing between these two sections of Sunni and Shiite communities are rooted in adoption of ‘takfeeri’ tradition practically though Shiite section would not like to own any tradition coming from Imam Ibn e Tammiyah.
The root cause of this takfeeri tradition lies in NOT distinguishing between what is disbelief/ ‘kufr’ and what is violation of our Nabi’s (s.a.w.w) sayings and commandments. Disbelief/ ‘kufr’ is NOT to believe in righteousness of sayings and deeds (both intellectual and physical) of our Nabi (s.a.w.w); a Muslim is that who believes in righteousness of sayings and deeds (both intellectual and physical) of our Nabi (s.a.w.w). Apart from believing in righteousness of sayings and deeds of our Nabi (s.a.w.w), a Muslim is also under obligation NOT to violate the sayings and deeds of our Nabi (s.a.w.w). But there is a difference between disbelieving in righteousness of sayings and deeds of our Nabi (s.a.w.w) and violating (not acting upon) the sayings and deeds of our Nabi (s.a.w.w). Disbelieving in righteousness of sayings and deeds of our Nabi (s.a.w.w) is ‘kufr’ and a person engaged in ‘kufr’ is ‘kafir’; but a person engaged in violating (not acting upon) the sayings and deeds of our Nabi (s.a.w.w) is not a ‘kafir’ though such a person can be called a sinner (for details plz see http://secondriseofislam.blogspot.com/2011/08/islam-emaan-and-qadyaniat.html). Quran says:
“O you who have believed, enter into Islam completely [and perfectly] and do not follow the footsteps of Satan. Indeed, he is to you a clear enemy” (al-baqra-208).
This verse addresses Muslims and says that Muslims should enter in Islam completely. It means the Muslims who do not act upon Islamic instructions completely are also Muslims. In other words, the Muslims whose practices are not in line with Islamic instructions are NOT ‘kafir’; rather they are Muslims though they are sinner Muslims.
The tendency of NOT distinguishing between ‘kufr’ and violation of religious instructions has led above mentioned two sections from Sunni and Shiite communities to adopt ‘takfeeri’ tradition to label their fellow Muslims as apostate/ ‘kafir’. These two sections from Sunni and Shiite communities have not flinched in applying this ‘takfeeri’ notion retrospectively to the period of companions of our Nabi (s.a.w.w). The specified Sunni section declares specified Shiite section as apostate/ kafir due to violation of our Nabi's (s.a.w.w) instructions, committed by such Shiite section, regarding our Nabi’s (s.a.w.w) companions; similarly specified Shiite section declares specified Sunni section as apostate due to the violations of our Nabi's (s.a.w.w) instructions, committed by such Sunni section, regarding our Nabi’s (s.a.w.w) some other companions. It may be appreciated that such violations committed by either section are not based on disbelief in the sayings and deeds of our Nabi (s.a.w.w). Rather most of such alleged violations are due to the fact that the violated instructions are not considered as rightly attributed to our Nabi (s.a.w.w) by either respective section (because both sections-Shiite and Sunni- follow different criterions for ascertainment of our Nabi's (s.a.w.w) sayings. It is not so in case of Qadyanis/Ahmadiyas; for better appreciation of Qadyani views, pls see http://secondriseofislam.blogspot.com/2011/08/islam-emaan-and- qadyaniat. html); similarly in other cases such alleged violations are violations of religious instructions passed by our Nabi (s.a.w.w). In this way each of mentioned sections from Sunni and Shiite communities declares the other section as ‘kafir’, NOT on the basis of condition of disbelief in righteousness of sayings and deeds of our Nabi (s.a.w.w);
The remedy of this ‘fasad’ originating from the Sunni-Shiite hostility may be sought in applying the distinction between Disbelief/ ‘kufr’ and violation of religious instructions, as explained above.