Narrated Ibn Abi Nu'm:
A person asked `Abdullah bin `Umar whether a Muslim could kill flies. I heard him saying (in reply). "The people of Iraq are asking about the killing of flies while they themselves murdered the son of the daughter of Allah's Messenger (s.a.w.a.) . The Prophet (S) said, They (i.e. Hasan and Husain) are my two sweet basils in this world."
Narrated Ibn Abi Na'm:
I was present when a man asked Ibn `Umar about the blood of mosquitoes. Ibn `Umar said, "From where are you?" The man replied. "From Iraq." Ibn `Umar said, "Look at that! he is asking me about the blood of Mosquitoes while they (the Iraqis ) have killed the (grand) son of the Prophet. I have heard the Prophet (S) saying, "They (Hasan and Husain) are my two sweet-smelling flowers in this world."
Narrated 'Abdur-Rahman bin Abu Nu'm:
that a man from the people of Al-'Iraq asked Ibn 'Umar about the blood of a gnat that gets on the clothes. Ibn 'Umar said "Look at this one, he asks about the blood of a gnat while they killed the son of the Messenger of Allah (S)! And I heard the Messenger of Allah (S) said: 'Indeed Al-Hasan and Al-Husain - they are my two sweet basils in the world.'"