Investigating the Hadith "Kill the Harmful One Before It Causes Harm"

Question

If during prayer a louse is seen crawling on one’s garment or body, is it permissible to kill it? For in the hadith it is said: “kill the harmful one before it causes harm” (qatl al-mu’dhi qabl al-idha’) — is it correct to kill it, or not?

Answer

In which book is the hadith “kill the harmful one before it causes harm” found? Please cite the reference and the chapter, and then an answer to the actual question will be possible. Editorial note: in the reports (athar) of Hazrat ‘Umar ibn al-Khattab ﵁ the killing of a louse during prayer is mentioned, and other hadiths ascribed to the Prophet ﷺ (marfu‘)

Source: Fatawa Mahmudiyya

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