Musannaf Ibn Abi Shayba 18:1249

Abu Bakr narrated to us, he said: Abbad bin al-Awwam narrated to us, from Sufyan bin Husayn, from Ibn Ashwa’, from al-Sha’bi, who said: There was fighting between two tribes of the Arabs, and some were killed from these and some from those. One of the two tribes said: "We will not be satisfied until a man is killed for a woman, and two men are killed for a man." The others refused them, so they took their case up to the Prophet, peace and blessings of Allah be upon him. He said: "The killing is *bara’*, meaning equal." He said: So the people reconciled among themselves regarding the blood money. He said: They calculated for the man the blood money of a man, for the woman the blood money of a woman, and for the slave the blood money of a slave, and it was only for one of the two tribes against the others. He said: This is His saying: "O you who have believed, prescribed for you is legal retribution for those murdered - the free for the free, the slave for the slave, and the female for the female." Sufyan said regarding: "But if the killer is forgiven by his brother at all," he said: If there is any remainder for him against his brother, "then let the seeking be done in a good manner and payment made to him with good conduct." [Continuing] to: "a painful punishment."