It was narrated from 'Aishah that the Prophet (ﷺ) said:
"The divorce of a slave woman is twice, and her (waiting) period is two menstrual cycles." Abu 'Asim said: "I mentioned this to Muzahir and said: 'Tell me what you told Ibn Juraij.' So he told me, narrating from Qasim from 'Aishah, that the Prophet (ﷺ) said: 'The divorce of a slave woman is twice, and her (waiting) period is two menstrual cycles."'
English reference: Vol. 3, Book 10, Hadith 2080
Arabic reference: Book 10, Hadith 2158