Hadith: Look at this man, he is asking me about the blood of mosquitoes, while they [Iraqis] killed the grandson of the Prophet (may Allah's peace and blessings be upon him). I heard the Prophet (may Allah's peace and blessings be upon him) say: They [his two grandsons] are my two flowers in this world

عن ابن أبي نعم، قال: كنتُ شاهدا لابن عمر، وسأله رجل عن دم البَعُوض، فقال: ممن أنت؟ فقال: من أهل العراق، قال: انظروا إلى هذا، يسألني عن دم البَعُوض، وقد قتلوا ابن النبي صلى الله عليه وسلم، وسمعتُ النبي صلى الله عليه وسلم يقول: «هما رَيْحَانَتاي من الدنيا».
[صحيح] - [رواه البخاري]

Ibn Abu Nu‘m reported: I saw Ibn ‘Umar when a man asked him about the blood of mosquitoes. Ibn ‘Umar asked: "Where are you from?" The man said: "From the people of Iraq." So he said: "Look at this man, he is asking me about the blood of mosquitoes, while they [Iraqis] killed the Prophet's grandson. I heard the Prophet (may Allah's peace and blessings be upon him) say: 'They [his two grandsons] are my two flowers in this world.'"
[Authentic hadith] - [Narrated by Bukhari]

Explanation

A man from Iraq came to Ibn ‘Umar (may Allah be pleased with him) and asked him: Is it permissible for a person in the state of Ihrām to kill harmful insects such as mosquitoes? Ibn ‘Umar was taken by surprise because the asker was concerned with such a trivial matter. Ibn ‘Umar was surprised by the question considering the man's background. He came from people who dared to commit major sins. So he said: ''Look at this man, he is asking me about the blood of mosquitoes, while they [Iraqis] killed the Prophet's grandson.'' So, they committed grave sins, yet showed that they feared Allah in their rituals. They even asked whether it was fine to kill mosquitoes. He then said: "I heard the Prophet (may Allah's peace and blessings be upon him) say: ‘They [his two grandsons] are my two flowers in this world.’” The Prophet (may Allah's peace and blessings be upon him) described his two grandsons as flowers, because he would kiss and smell them, as if they were among the sweet-smelling things that people enjoy in this world.