Musannaf Ibn Abi Shayba 19:924

Abu Bakr narrated to us, he said: Abd al-Rahim ibn Sulayman narrated to us, from Ash'ath, from al-Hasan, who said: Do not kill women if they apostatize from Islam, but they are to be invited to Islam. If they refuse, they are to be taken captive and made slave-women of the Muslims, and they are not to be killed.