The Messenger of Allah ﷺ said, "A Muslim is the brother of another Muslim. He does not wrong him, nor abandon him, nor look down on him. It is evil enough for a man to look down on his Muslim brother."
حدثنا يحيى بن آدم حدثنا سفيان عن داود بن قيس عن أبي سعيد
قال رسول الله ﷺ المسلم أخو المسلم لا يظلمه ولا يخذله ولا يحقره وحسب امرئ من الشر أن يحقر أخاه المسلم
Its isnad is sahih. Sufyan is Thawri. Abu Saeed is the freedman of Abdullah bin Amir bin Kurayz. The hadith appears in Jami al-Masanid wal-Sunan 7:445, taken from this very place. It is an abridgment of 7713, and we have already pointed this out there.