Narrated by Abu Bakra (ra) Allah’s messenger (saw) said: “Shall I inform you of the greatest sins and in another variation he repeated this three times. We the companions said, “Certainly, O messenger of Allah! He (saw) said: “Associating anyone with Allah, disobedience to parents”. The prophet sat up straight after he had reclined and added, “And I warn you against false utterance and false witness, “And I warn you against false utterance and false witness”. The messenger of Allah (saw) kept saying that warning until we thought that he would not stop”. Bukhari & Muslim.