Abdullah ibne-Amr ibnil As Radiyallahu anhuma narrates
that Rasullullah Sallallahu alaihi wasallam said:
It is a major sin that a man slanders his parents.
The Sahabah (Radhiyallaho anhum) asked:
O Rasulallah! (Sallallahu alaihi wasallam)
Could a person slander his own parents?
Rasullullah Sallallahu alaihi wasallam answered:
Yes, if he slanders another person¢s father,
the latter would slander his father
and if he slanders someone,s mother,
the latter in turn, would slander his mother.
(Muslim)