It was narrated from 'Abdullah bin 'Amr that the Messenger of Allah (ﷺ) said:“Whoever kills a Mu'ahid, will not smell the fragrance of Paradise, even though its fragrance may be detected from a distance of forty years.”
Hadith No. 2686
Sunan Ibn Majah
Gradings:
Al-Albani:
Sahih
Muhammad Fouad Abd al-Baqi:
Sahih
Zubair Ali Zai:
Sahih Bukhari