Musannaf Ibn Abi Shayba 19:908

Abu Bakr narrated to us, he said: 'Abdah bin Sulayman narrated to us, from Ubaydullah, from Nafi', from Ibn Umar, that a slave girl of Hafsah bewitched her. They found her witchcraft and she confessed to it. So, Abd al-Rahman bin Zayd ordered [her execution], and he killed her. This reached Uthman, and he disapproved of it and it was severe upon him. Ibn Umar came to him and informed him that she had bewitched her, that she had confessed to it, and that they had found her witchcraft. It was as if Uthman had only disapproved of that because she was killed without his permission.