The ruling authorities were afraid of the Imam's school, for it became larger; many people attended it, studied the Imam's science, told the others about it, spread the merits and outstanding qualities of Ahl al-Bayt. These things made al-Mansur sleepless and he had fear for his political interests. He was fearful because he thought that the people would admire Imam al-Sadiq, so he entrusted Abu Hanifa with testing the Imam through the most difficult and ambiguous questions. Now, we will let Abu Hanifa tell us of that: "I have never seen anyone more knowledgeable than Ja'far b. Muhammed. When al-Mansur brought him, he sent for me and said: 'Abu Hanifa, the people have admired Ja'far b. Muhammed. So prepare for him difficult questions.' I prepared for him forty questions. Then he sent for Ja'far when he was in al-Hira. He brought him and I came in to him. Ja'far b. Muhammed was on his right hand. When I looked at him, I venerated him more than I venerated Abu Ja'far al-Mansur. I greeted al-Mansur and he asked me to sit down. He turned to him (Imam al-Sadiq) and said to him: 'Abu 'Abd Allah, this is Abu Hanifa!' 'Yes, I know him', he, peace be on him, replied.
"Then al-Mansur turned to me and said: 'Abu Hanifa, ask Abu 'Abd Allah about your questions.' I asked him about them and he answered me, saying: 'You say so-and-so; the people of Medina say so-and-so; we say so-and-so. Perhaps we follow (you and them) and perhaps we oppose (you and them). I asked him about the forty questions and he showed no defect in any of them.'" ( Al-Dhahabi, Tadhkirat al-Hafiz.)