Hesham Debates with Yehya Bin Khalid al-Bermeki

Yehya b. Khalid questioned Hisham in the presence of Harun al-Rashid, saying to him:
-O Hisham, tell me of the truth: Could it be in two different directions?
-Tell me about two persons who dispute with each other and differ over the precept of the religion: Are they right or wrong? Is one of them right and the other wrong?
-They are not void of that; it is not permissible that they both are right.
-Tell me about (Imam) ‘Ali and al-‘Abbas when they sued one another about the inheritance before Abu Bakr: Who was the right and who was the wrong?
Hisham became perplexed; he narrated his perplexity, saying: “If I had said that ‘Ali was wrong, then I would have been unbeliever and withdrawn from me creed. If I had said that al-‘Abbas was wrong, al-Rashid would have cut off my head.” It was really a problem. Shortly after that he remembered the saying of Imam al-Sadiq, peace be on him: “O Hisham, you are still supported by the Holy Spirit as long as you support us with your tongue.” So he came to know that he would not be deserted. He found an answer and said to him: “No mistake issued from them; they both were right. There is (an example) similar to this in the Qur’an. Allah, may His name be great, says in the story of Dawud: And has there come to you the story of the litigants, when they made an entry into the private chamber by ascending over the walls...two litigants, of whom one has acted wrongfully towards the other. Which of the two angels was wrong? And which of them was right? If you said that they both were wrong, then your answer would be similar to my answer itself.”
Yehya replied: “I do not say that the two angels were wrong; rather I say that they both were right. That is because they really did not sued one another, nor did they differ over the judgment. They showed that to draw Dawud’s attention to his mistake, to make him know the judgment, and to inform him of it.”
As a result Hisham said: “So were ‘Ali and al-‘Abbas; they did not differ over the judgment, nor did they really sue one another. They showed the difference and the dispute, that they might draw Abu Bakr’s attention to his error and inform him of his mistake and show him the way to his wronging them in respect with the inheritance. They had no doubt about their affair. They did just as the two angels did.”
Accordingly, Yehya was perplexed and was unable to give an answer. As for al-Rashid, he approved this wonderful explanation Hisham concluded. (  Al-Fusool al-Mukhtara, vol. 1, pp. 24-25. This debate has been briefly mentioned in the book 'Uyun al-Akhbar, vol. 2, p. 15.)