The scholar Abu Mohammad Hasan bin Husain bin Babeweyh, narrated from the blessed scholar Abu Jaafar Mohammad bin Hasan Al-Tousi, from the great scholar Abu Abdillah Mohammad bin Mohammad bin No’man, from the blessed scholar Abu Jaafar Mohammad bin Ali bin Husain bin Babewyeh, from his father, from Saad bin Abdullah, from Ahmad bin Mohammad bin Isa, from MOHAMMAD BIN ALI Al-Baqir (ASWS), from his FATHERS (ASWS), who said:
The MESSENGER OF ALLAH (SWT) said to ALI BIN ABI TALEB (ASWS), “Write what I dictate to you.”
ALI (ASWS) said, “O MESSENGER OF ALLAH (SAWW)! Are you worried that I will forget?”
The PROPHET (SAWW) replied, “No, I am not worried that you will forget. I have asked ALLAH (SWT) to protect your memory and you will not forget anything. But write what I tell you for your partners.”
ALI (ASWS) said, “Who are my partners?” The PROPHET (SAWW) replied:
They are the IMAMS (ASWS) from your sons. ALLAH (SWT) pours the rains of His Mercy on my nation through them; ALLAH (SWT) will answer the prayers of my nation through them; ALLAH (SWT) keeps the evil away from my nation through them; And ALLAH (SWT) will descend His Mercy on people through them. Then the PROPHET (SAWW) pointed to HASAN (ASWS) and said, “He is the first Imam after you.”
Then he pointed to HUSAIN (ASWS) and said, “The Imams are from his sons.”
(Ref: Amaali Of Sadouq 327)
Note: The above Hadees does not mean that the other Imams (as) forget because as the Holy PROPHET (saww) has said that all of them are Mohammed (as) from the same noor. Its just a statement for them.