I heard Anas b. Malik saying: The Messenger of Allah (ﷺ) talked about the major sins, or he was asked about the major sins. Upon this he observed: Associating anyone with Allah, killing of a person, disobedience to parents. He (the Prophet further) said: Should I not inform you about the gravest of the major sins, and (in this connection) observed: False utterance or false testimony. Shu'ba said. It was most probably" false testimony".
Reference: Sahih Muslim 88 b In-book : Book 1, Hadith 167 USC-MSA web (English) : Book 1, Hadith 160 (deprecated)
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