The Greatness of Crying for Imam Hussain, peace be upon him

There’s a village called Musayyib near Najaf where the two rivers of Euphrates and Tigris meet. A Shii man would pass by the village for visiting Amir al-Mu’mineen, Imam Ali, peace be upon him. A man living in that village would make fun of the Shii man whenever he would pass by, since he knew that the man is going to visit Imam Ali, peace be upon him. He even insulted Amir al-Mu’mineen once and also said: “Tell him (Imam Ali) to destroy me, otherwise I will kill you when you return! The Shii man got really upset. He expressed his impatience when he went for ziarah, and said to the Imam: “You know what this opposing man is doing; why don’t you respond to him?! He saw the Imam in a dream and complained to him. Amir al-Mu’mineen, peace be upon him, said: “He has a right upon us for which we cannot punish him in this world.” The Shii man said: “I suppose it’s for the insults that he does that he has gained rights upon you!
The Imam said: “Once he was sitting at the place where the Euphrates and Tigris meet, looking at the Euphrates, when suddenly the event of Karbala and the prohibition of water from Imam Hussain, peace be upon him, came to his mind; he said to himself: ‘Omar Sa’d didn’t do good by killing them thirsty.’ He got upset and a drop of tear came down from his eyes. Therefore he has a right upon us that we cannot punish him in this world.”
The Shii man says: “I woke up and went towards my own house. I met the Sunni man along my way. He said while mocking me: “Did you see your Imam and did you send my message to him? The Shii man said: “Yes, I did and I have a message for you.” He laughed and said: “Tell me what is it?” The Shii man explained the whole story. The Sunni man put his head down when he heard the story, pondered a little and said: “O God, there was no one there at that time and I haven’t told anyone about it; how did Ali know?! He then became Shia.