Narrated 'Abdullah bin 'Amr : Allah's Apostle (Salla Allahu Alyhe Wa Aalihe Wassalam ) said,
"It is one of the greatest sins that a man should curse his parents.
It was asked(by the Prophet),
"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."
Book :73 (Good manners and form(Al-Adab)