Uthman bin Sa’eed al-Umari

Ahmad bin Isaaq bin Sa’d al-Qummi said, ‘‘One day, I went to Abul Hasan Ali bin Muhammad (Imam al-Hadi) (blessings be on him) and said to him: O my master, some times I am here and some times I am not. I cannot come to you at every time. Whose sayings do we accept and whose orders do we follow?’
He said, ‘This is Abu Amr the trustworthy, the faithful. Whatever he says to you is from me and whatever he informs you of is in behalf of me.’
When Abul Hasan (a.s.) died, I referred to his son Abu Muhammad al-Hasan al-Askari (a.s.) and asked him one day as I had asked his father before. He said to me, ‘This is Abu Amr the trustworthy, the faithful. He is the trust of the formers and my trust in life and death. Whatever he says to you is from me and whatever he informs you of is in behalf of me.’
Ahmad bin Isaaq also said, ‘I asked Abul Hasan (a.s.): with whom shall I deal and from whom shall I take (religious rulings), and whose saying shall I accept? He said to me, ‘Al-Umary my trust; whatever he informs you of is on behalf of me and whatever he says to you is on behalf of me. Listen and obey him, for he is trustworthy and reliable.’