The Messenger of Allah ﷺ said, "It is enough evil for a person to despise his Muslim brother. Every Muslim is sacred to another Muslim, his blood, his wealth, and his honor."
قال رسول الله ﷺ: حسب امرئ من الشر أن يحقر أخاه المسلم، كل المسلم على المسلم حرام، دمه، وماله وعرضه.
Muslim narrated it in the Book of Righteousness and Kinship Ties (2564:32) from Abdullah bin Maslama bin Qanab, who said, Dawud, meaning Ibn Qays, narrated to us, from Abu Saeed, the freedman of Amir bin Kurayz, from Abu Hurairah, who said, and he mentioned it in a long hadith.The meaning of his saying, "It is enough evil for a person" is that it suffices as evil for him to hold a Muslim in contempt, meaning that if evil were something sought after, this amount of it would be sufficient. This conveys how grave a matter it is.