Musannaf Ibn Abi Shayba 3:3863

Ali ibn Mushir narrated to us, from al-Mukhtar ibn Fulful, from Anas ibn Malik, who said: A slave woman whom he (Umar) used to recognize as belonging to some of the Emigrants (Muhajirun) or the Helpers (Ansar) entered upon Umar ibn al-Khattab, and she was wearing a *jilbab* and was veiled with it. He asked her, "Have you been emancipated?" She said, "No." He said, "Then what is the matter with the *jilbab*? Take it off your head. The *jilbab* is only for the free women among the believing women." She hesitated, so he stood up to her with his whip (*durra*) and struck her with it on her head until she cast it off her head.