Abd al-Rahman bin Abi al-Zinad (may Allah have mercy on him) narrates from his father (may Allah have mercy on him), and he from the jurists, that judgement is not to be given by an oath and a witness in divorce, 'itaq (freeing a slave) or separation. They did not consider the testimony of women valid when no man was with them, except in what only women see, and they used to say: Whoever has a witness testify for him about the killing of his slave, he swears one oath along with his witness and becomes entitled to the value of his slave.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الشهادات / 20691