Riyad as-Salihin
Riyad as-Salihin 1576
Prohibition of Despising Muslims
Arabic hadith text
وعن جُندب بن عبد الله رضي الله عنه قال: قال رسول الله صلى الله عليه وسلم : "قال رجل: والله لا يغفر الله لفلان، فقال الله عز وجل: من ذا الذي يتألى علي أن لا أغفر لفلان! فإني قد غفرت له، وأحبطت عملك" ((رواه مسلم)).
Translation
Jundub bin 'Abdullah (May Allah be pleased with him) reported
The Messenger of Allah (ﷺ) said, "Once someone said: 'By Allah! Allah will not forgive such and such (a person).' Thereupon Allah, the Exalted and the Glorious, said: 'Who is he who takes an oath in My Name that I will not grant pardon to so-and-so? I have granted pardon to so-and-so and rendered your good deeds fruitless."'[Muslim].