The Prophet (ﷺ) said thrice, "Should I inform you about the greatest of the great sins?" They said, "Yes, O Allâh's Messenger (ﷺ)! " He said, (1) To join others in worship with Allâh, and (2) to be undutiful to one's parents. The Prophet (ﷺ) then sat up after he had been reclining (on a pillow) and said, (3) And I warn you against giving a lying speech (false statement) ", and he kept on saying that warning till we thought he would not stop. [3:822-0.B]