Hazrat Abdullah bin Amr narrates that the Noble Prophet (peace and blessings be upon him) said: Surely, the greatest sin in the sight of Allah is that a person abuses his parents. The companions asked: How can a person abuse his parents? The Prophet (peace and blessings be upon him) replied: He abuses another person's father, so that person, in return, abuses his father. He abuses another person's mother, so that person, in return, abuses his mother.