In a field opposite his palace, Mutawakkil had kept in captivity many man-eating wild animals like lions, tigers, leopards and bears etc. A very high wall surrounded this field. The field was known as Barkatul Saba. When Mutawakkil used to be extremely angry with a criminal, he was pushed into this enclosure. The beasts inside used to pounce on him and finish him off in no time.
One day Mutawakkil summoned Imam Ali Naqi (a.s) and said to him, “I have heard that you are instigating people to revolt against me.” Imam (a.s) said, “Whoever has conveyed this has given you incorrect information. I have never taken part in any political matter.” He said, “You are trying to fool me.” Imam (a.s) became angry at this allegation and he said, “Do you consider me like yourself? We are Ahl ul-Bayt of the Messenger. We never resort to intrigue.” Mutawakkil ordered him to be thrown to the beasts, and he himself went to the terrace of his palace to watch the drama. The slaves tried to forcibly take Imam (a.s) to the enclosure of the wild animals but he said, “There is no need to apply force, I will go there myself.” The Holy Imam walked with absolute tranquility and opening the door of the enclosure stepped inside. All those who witnessed this daring were shocked. As soon as he reached inside all the beasts gathered around him and wagging their tails fell down at his feet, while the Imam caressed their heads and backs in affection. After this Imam (a.s) calmly spread his prayer mat and performed Prayer. The beasts surrounded him in a circle and watched his dignified worship. Seeing this, Mutawakkil was bewildered and he had to face intense regret.
Reference :Akhlaq al-A’imma, Morals & Manners of the Holy Imams