Sahih Muslim Book 32, Hadith Number 6256.
Chapter : Help your brother whether he is an oppressor or an oppressed one.
Jabir b. ‘Abdullah reported that a person from the emigrants struck the back of an Ansari. He came to Allah’s Apostle (may peace be upon him) and asked for compensation. Thereupon Allah’s Apostle (may peace be upon him) said: Leave it; for it is something disgusting. Ibn Mansur said that in the narration transmitted on the authority of Amr (these words are also found): “I heard Jabir.”