Session 183-Ali ibn Abu Talib(ra)-The only time where there was absolute unity amongst the believers

Alee ibn Abu Talib (ra) Session 183 The only time where there was absolute unity amongst the believers was in the appointment of Uthmaan (ra). Who did Umar (ra) refer to and wash his hands off, called them unbelievers and enemies of Allah سبحانه وتعالىٰ?