´'Abdur-Rahman bin Abi Bakrah narrated from his father who said:` " The messenger of Allah said: 'Shall I not tell you of the biggest of the major sins?' they said : 'Of course! O Messenger of Allah!' He said: 'To join partners with Allah, and disobeying one's parents.'"He said : " He sat up, and he had been reclining. He said: 'And false testimony, or false speech.' And the Messenger of Allah would not stop saying it until we said (to ourselves): 'I wish that he would stop.'"
Hadith Referenceسنن ترمذي / كتاب البر والصلة عن رسول الله صلى الله عليه وسلم / 1901
´'Abdullah bin 'Amr narrated that :` the Messenger of Allah said: "It is among the greatest of sins that a man should curse his parents." They said: "O Messenger of Allah! Does a man curse his parents?" He said: "Yes. He verbally abuses the father of a man, who in turn, verbally abuses his father, and he (retaliates and) curses his mother , so he curses his mother."
Hadith Referenceسنن ترمذي / كتاب البر والصلة عن رسول الله صلى الله عليه وسلم / 1902