Musannaf Ibn Abi Shayba 18:1299

Abu Bakr narrated to us, he said: Jarir narrated to us, from Mughira, from Ibrahim, and from Hammad, from Ibrahim regarding two slaves, one of whom gouges out the eye of his companion. He said: If their values are equal, then it is an eye for an eye. And if the value of one of them is greater than the other, the one with the greater value shall pay the difference to the one with the lesser value.