A Christian who had committed fornication with a Muslim woman was brought to Mutawakkil. When Mutawakkil wanted to sentence him, he became a Muslim. Qazi Yahya said that he could not be sentenced now, because his conversion has remitted all his past sins. Someone suggested that the opinion of the master of the faithful, Imam Ali Naqi (a.s) might also be obtained in this matter. Thus Mutawakkil sent someone to him to inquire about this. He said, “He should be beaten till he dies.” The court scholars refused to accept this verdict and demanded justification. Again the Imam was petitioned and he said, “A clear verse is there regarding this: But when they saw Our punishment, they said:
We believe in Allah alone and we deny what we used to associate with Him. ( Surah Momin 40:84)
Reference :Akhlaq al-A’imma, Morals & Manners of the Holy Imams