question #2 Sahih Muslim 88b, Book 1, Hadith 167 : Why is false testimony considered one of the gravest major sins in Islam?

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”.