On the authority of Abū Hurayrah (May Allah be pleased with him) that the Messenger of Allah (may the blessings and peace of Allah be upon him) said:
The gates of Paradise will be opened on Mondays and on Thursdays, and every servant [of Allah] who associates nothing with Allah will be forgiven, except for the man who has a grudge against his brother. [About them] it will be said: Delay these two until they are reconciled; delay these two until they are reconciled; delay these two until they are reconciled.
It was related by Muslim (also by Mālik and Abu Dāwūd).
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Note: By the term, "Brothers" used in the Hadith, it is meant as brothers in Islam. And this goes for females against females or females against males or males against females. Basically, anyone within this Ummah holding a grudge against another of this Ummah.
