Sahih Bukhari

Narrated Abu Bakra:The Prophet (ﷺ) said thrice, ""Should I inform you about the greatest of the great sins?"" They said, ""Yes, O Allah's Messenger (ﷺ)!"" He said, ""To join others in worship with Allah and to be undutiful to one's parents."" The Prophet (ﷺ) then sat up after he had been reclining (on a pillow) and said, ""And I warn you against giving a false witness, and he kept on saying that warning till we thought he would not stop. (See Hadith No. 7, Vol)