Sahih Al Bukhari – Book of Good Manners And Form (Al-Adab)

Volumn 008, Book 073, Hadith Number 004.
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Narated By 'Abdullah bin 'Amr : Allah's Apostle said. "It is one of the greatest sins that a man should curse his parents." It was asked (by the people), "O Allah's Apostle! How does a man curse his parents?" The Prophet said, "'The man abuses the father of another man and the latter abuses the father of the former and abuses his mother."

Junaid

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