The Prophet ﷺ forbade the earnings of female slaves.
نهي النبي ﷺ عن كسب الإماء.
No references are available.
Bukhari narrated it in the Book of Hiring (2283), from Muslim bin Ibrahim, who said, Shubah told us, from Muhammad bin Jahada, from Abu Hazim, from Abu Hurairah, and he related it.Ibn Hibban also narrated it in his Sahih (5159) through Shubah's chain, adding at the end, "for fear that they might commit fornication." If this addition is preserved, then what is meant by earning here is fornication, not work in general.