God's Chastisement to those who Speak ill of him
Saeed bin Musayyib narrates that a man was once speaking ill of Hazrat Ali (ra), Hazrat Talha (ra) and Hazrat Zubair (ra). Hazrat Sa‘d (ra) bin Malik, i.e., Hazrat Sa‘d bin Abi Waqas stopped him, saying, “Do not revile my brothers,” however, the man did not desist. Hazrat Sa‘d stood up and offered two rak‘ah [unit] of prayer and offered the following supplication, “O Allah! If these things that he is saying are a means of incurring Your wrath, then send down your chastisement upon him in front of me so that he can be a lesson to others.” Thus, as soon as this individual left the gathering, a camel was charging towards him. The camel caught him in a rocky terrain and throwing him underneath, crushed him, thereby killing him. The narrator states that the people went to Hazrat Sa‘d saying, “O Abu Ishaq! Rejoice for your prayer has been accepted.”
(Usdul Ghabah, Vol. 3, p. 88, Talha bin Ubaidillah Quraishi, Dar-ul-Kutub al-Ilmiyyah, Beirut)