This Is My Faith - Al-fatlawi, Ali - الصفحة ٣٧٦ - What is Shi’ism?
Shi’ite idiomatically means the followers of Amir Al-Mu’menin (PBUH) who give preference to him over others; so, the followers and the supporters and the defenders and the loyal partisan of Imam Ali Bin Abu Talib (PBUH).
We have evidence from the Hadith in this regard. It is reported, in ‘Tafsir Al-Safi’, from Al-Amali that Jabir Bin Abdullah said: “We were with the Prophet (PBUH) when Ali Bin Abu Talib arrived. So, the Prophet (PBUH) said: ‘my brother has come’, then he turned to Ka’ba, struck it and said: ‘By He who has my life, this man and his followers (Shi’a) are the victorious in the Day of Judgment.’
He added: ‘He is the first to believe with me among you and the most loyal towards the vows to Allah, the most committed to the commands of Allah, the most objective and just towards people, the most straightforward and of most advantages to Allah.’ Then, he mentioned this Holy Verse:
(As for those who believe and do good, surely they are the best of men)٩٨;٧.