Ibn Abbas who says that one day I was seated in the presence of the Holy Prophet (S) when Imam Hasan (a.s.) came. When the Prophet’s sight fell on him, he started weeping and then said,
“Come to me, come to me”
and made him sit on his right thigh. After some time Imam Husayn (a.s.) came and the Prophet (S) after looking at him started weeping. Then he made Imam Husayn sit on his left thigh. Then after some time Hazrat Fatima (a.s.) came and the Prophet again started weeping and repeated as before and told her to sit facing him. Then when Imam Ali (a.s.) came he started weeping and repeating his words signaled him to sit on his right side. When the companions, who were sitting there saw this, they said, “O Prophet of Allah! You have not seen anyone among them except that you have wept, is there none among them whose sight could make you happy”? The Prophet replied,
“I swear by Him Who has exalted me to Prophethood and has elevated me above the entire creation! No one on the entire earth is more dear to me than them. While my weeping is the result of the sufferings which shall befall them after my death. And I recollect the oppression which shall befall my son Husayn. It is as if I see him taking refuge under the shelter of my grave or the Sacred Sanctuary (Ka’bah), but no one will let him halt there. He will then go to the place which is the spot of his Martyrdom and grief and trials. While a group of men will assist him, who will be the leaders of all Martyrs among my people on the day of Judgment. It is as if I see that arrows are shot at him and he has fallen down upon the earth of perdition from his steed. Then they will slaughter him like a sheep in an oppressive manner.”
Then he started weeping and wailing and all those near him too wept and their voices increased. Then he arose and said,
“O Allah, I complain to you about all those sufferings which my progeny will have to bear after my death.”
Reference : Nafasul Mahmoom – Shaikh abbas Qummi (r.a.)