Three of the worst major sins: polytheism, disrespecting parents, and false witness
Narrated Abdur-Rahman b. Abu Bakra that his father said: We were with the Messenger of Allah, peace be upon him, and he said: “Shall I not tell you about the biggest enormities (major sins)? They are three: Idolatry against Allah, disobedience to parents, and false witness (lies).” The Messenger of Allah was reclining and then he sat up and continued saying it until we wished he would stop.
[Sahih Muslim, Book 001, Number 0158]
