(22) باب مَنَاقِبُ الْحَسَنِ وَالْحُسَيْنِ رضى الله عنهما
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 (ﷺ) . The Prophet (ﷺ) said, They (i.e. Hasan and Husain) are my two sweet basils in this world."
Reference: Sahih al-Bukhari 3753
In-book reference: Book 62, Hadith 100
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 5, Book 57, Hadith 96