Ali (ra) was the one of the companions and also the son in law of the prophet (pbuh). He must have without any doubt followed the same practices (sunnah) in the religion as our prophet (pbuh) did. How can shias who consider Ali (ra) as first Khalifa has a total different ways of practising Islam? Who change Islam for them? How they come to these practices?
Brief detail please.
The sources of the various kinds of practices in the Muslim sects is the various kinds of information reported in narratives ascribed to the Prophet (pbuh) and his various companions or any actions ascribed to the Prophet (pbuh) and his various companions in these narratives. As for the Shiites, the sources of their actions, besides those mentioned above, are also the practices ascribed to their various Imams (including Ali). In most of the cases, the ascribed variations should have been interpreted as allowable variations in the prescribed practices. However, unfortunately, the Muslim sects generally interpreted their preferred variation as the only correct method of carrying out a particular practice. This, somewhat strict interpretation of the ascribed variations resulted in the tragic formation of the Muslim sects and sub-sects.
Thus, even though I agree with you that the companions of the Prophet (pbuh) – including Ali (ra) – must indeed have adhered to the practices of the Prophet (pbuh), in letter and spirit, yet because there are certain variations ascribed to the Prophet (pbuh) and his various companions, these variations have provided the basis of the variations that exist in the practices of the various Muslim sects.
I hope this helps.
January 18, 2002