Musnad Ahmad 25:1108

Zayd ibn al-Hubab narrated to us, Sayf ibn Sulayman al-Makki informed me, from Qays ibn Sa’d al-Makki, from ‘Amr ibn Dinar, from Ibn ‘Abbas, that the Prophet (peace and blessings of Allah be upon him) "judged by an oath and a witness." Zayd ibn al-Hubab said: I asked Malik ibn Anas about the oath and the witness: Is it permissible in divorce and manumission? He said: "No, this is only in buying and selling, and the likes thereof."