What did the Prophet Muhammad (saw) say were the most grievous of the grave sins?
 It is narrated on the authority of 'Abdur-Rahman b. Abu Bakra that his father said:                      We were in the company of the Messenger of Allah (may peace be upon him) that he observed: Should I not inform you about the most grievous of the grave sins? (The Holy Prophet) repeated it three times, and then said: Associating anyone with Allah, disobedience to parents, false testimony or false utterance. The Holy Prophet was reclining, then he sat up, and he repeated it so many times that we wished that he should become silent.