There is a Joy in Forgiveness in which You cannot Find in Revenge
A man related to Imam Sajjad (as) came to him, and started cursing the Imam.
Imam Sajjad (as) did not answer the man. When the man left, Imam Sajjad (as) said to his companions, "you have heard what this man said to me; I would like you to come with me so that you can hear my reply to him."
The companions replied, "We will come with you, for we would like you to answer him back. We too would like to say something to him."
Imam Sajjad (as) put on his shoes and he read this verse as he began to leave, ﴾...Those who lower and suppress their anger, yet forgive people, truly Allah loves them.(3:134)﴿
Hearing that, the companions of Imam Sajjad (as) understood that the Imam will not answer the man back.
They walked towards the man’s house till they reached to his door. With a loud voice Imam (as) said, "Tell him Ali-ibn al-Hussain is here." The man came out offensively prepared to face the punishment of Imam Sajjad (as). But Imam Sajjad (as) told the man, "My Brother! A few moments ago you came to me, and you said whatever you wished.
If what you said about me is true within me, then I will ask Allah for forgiveness; and if what you said is not within me, then May Allah forgive you."
At that time the man kissed Imam Sajjad’s (as) forehead and said: "I said something about you that is not in you, yet I deserve whatever I said to you."
* Selection from "al-Irshad", by Sheikh Mofid, vol. 2, p.145