He was the deputy of the people of Qum. He narrated traditions from Abu Ja’far the Second (Imam al-Jawad) and from Abul Hasan (Imam al- Hadi) (peace be on them). He was from the close companions of Imam Abu Muhammad (a.s.). He had written some books such as “Ilal as- Sawm: causes of fasting” and “Masa’il ar-Rijal: questions of men” which he had collected from Abul Hasan the Third (Imam ar-Redha) (a.s.).
Sheikh at-Toosi said he was one from those who had met Imam al- Mahdi (a.s.)
Muhammad bin Ahmed bin as-Salt al-Qummi wrote a letter to ad-Dar (to the imam) and mentioned in it the story of Ahmed bin Isaaq al- Qummi and his companionship. He mentioned that he wanted to perform Hajj and needed one thousand dinars. He said in the letter, ‘If my master sees that he orders to lend him this amount and get it back from him in his country when he comes back, I shall do it (give him the money).’ The imam (a.s.) replied, ‘It is a gift from us to him and when he comes back, he will get another gift from us.’This story showed his faith and the respect of the imam (a.s.) towards him.
Abdullah bin Ja’far al-Himyari said, ‘Once, Sheikh Abu Amr (may Allah have mercy on him) and I met Ahmad bin Isaaq, who signaled to me to ask Abu Amr about the Successor (Imam al-Mahdi). I said to him, ‘O Abu Amr, I want to ask you about something that I have no doubt about.’ He said, ‘Ask about what you want!’ I said to him, ‘Did you see the Successor after Abu Muhammad (a.s.)?’ He said, ‘By Allah, yes.’
Anyhow, this man was reliable and had a high position near the Ahlul Bayt (a.s).