It was narrated from Salamah bin Muhabbiq that:
the case of a man who had intercourse with the slave woman of his wife was referred to the Messenger of Allah (ﷺ), and he did not stipulate any legal punishment for him. (PT)
English reference (PT): Vol. 3, Book 20, Hadith 2552 (PT)
Arabic reference (PT): Book 20, Hadith 2649 (PT)