Knowledgeable scholar Abu Ali Hasan bin Abi Jaafar Al-Tousi narrated from his blessed father Abu Jaafar Mohammad bin Hasan Al-Tousi, from the great scholar Abu Abdillah Mohammad bin Mohammad bin No’man Al-Harethi Al-Baghdadi, from Abul Qasem Jaafar bin Mohammad bin Qulaweyh, from his father, from Saad bin Abdullah, from Ahmad bin Mohammad, from Abbas bin Maaroof, from Mohammad bin Sanan, from T’alha bin Zaid, from jaafar bin Mohammad, from his father, from his grandfather from the MESSENGER OF ALLAH (SAWW), who said:
ALLAH (SWT) has never taken back the life of any of His Prophet without first ordering them to appoint the best man from their family as their successor, and now ALLAH (SWT) has ordered me to appoint a successor.
I asked ALLAH (SWT), “Whom should I appoint to be my successor?”
ALLAH (SWT) replied:
Appoint your cousin, ALI BIN ABI TALEB (ASWS) . I have mentioned his name in the previous books. I wrote in the books that ALI (ASWS) is your heir and I took the covenant based on this.
The covenant that I took from My creation and My prophet entailed accepting Me as ALLAH (SWT) , accepting you as the MESSENGER (SAWW) , and accepting ALI BIN ABI TALEB (ASWS) as the Wali.
(Amaali of Tousi 1:102. Bihar Al Anwar 15:18. 26:271, 38:111, Taawil Al-Ayaat 2:566.)