Abu Hanifa was on top of those who believed in compulsion; he traveled to Yethrib (Medina) to debate with Imam al-Sadiq, peace be on him, on this belief, while he was famous for his being the opponent of it. When he arrived in it, he headed for the Imam's house. He sat in the corridor waiting for a permission to enter. While he was sitting there, a boy came out walking slowly. He asked the boy: "Where does the stranger relieve nature?"
The boy turned to him and said to him: "Slowly!" Then he sat down politely, leaned against the wall, and began to give him an answer to his question, saying: "Avoid the banks of rivers, the places where fruit fall, the courtyards of mosques, and the middle of a road. Hide yourself behind a wall; you should not face the qibla (direction to the Kaaba) nor have your back towards it; and relieve nature where you wish." He explained to him the places where it is detested or forbidden to relieve nature, so Abu Hanifa was dazzled and astonished because he had not thought that there was a boy who had such a scientific ability.
"What is your name?" asked Abu Hanifa.
"Musa b. Ja'far b. Muhammed b. 'Ali b. al-Husayn b. 'Ali b. Abi Talib," was the answer.
When Abu Hanifa came to know that the boy was a branch of the Tree of the Prophecy and the Imamate, he became tranquil, and then he asked him about the question he had prepared for Imam al-Sadiq, saying: " Boy, from whom does disobedience (issue)? Does it issue from Allah or from the servant?"
The Imam answered him, saying: "Either it issues from Allah and not from the servant at all, so Allah does not punish the servant for what he does not do; or it issues from the servant and Allah, and Allah is a stronger partner. Therefore, the stronger partner has no right to punish the weak for a sin in which they are equal; or it issues form the servant and not from Allah. So If He wills to pardon (him), (He will pardon him), and If He wills to punish (him), (He will punish him); and Allah is He whose help is sought." According to the rational restriction, this conclusion is full of all the elements of the firm scientific proofs man cannot invalidate or refute.
Abu Hanifa became dazzled and astonished, so he raised his voice, saying: "I am satisfied with what I have heard!"
He went out defeated; inability appeared on his face. He did not met with Imam al-Sadiq (as)