Musnad Ahmad 30:1601

Isma'il ibn 'Umar and Abu Nu'aym narrated to us, they said: Dawud ibn Qays narrated to us, Abu Sa'id, the freed slave of 'Abdullah ibn 'Amir ibn Kurayz, narrated to me, from Abu Hurayrah, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Do not outbid one another (to deceive), do not hate one another, do not turn your backs on one another, do not envy one another, and let not some of you sell over the sale of others. And be, O servants of Allah, brothers. The Muslim is the brother of the Muslim; he does not wrong him, he does not belittle him, and he does not forsake him. Everything of the Muslim is sacred to the Muslim: his blood—Isma'il said in his narration: and his wealth, and his honor. Righteousness is here, righteousness is here, righteousness is here—pointing to his chest three times. It is sufficient evil for a man that he belittles his Muslim brother."