Sahih Muslim 1703a
Abu Huraira reported that he heard Messenger of Allah ﷺ as saying: When the slave-woman of any of you commits adultery and this (offence of hers) becomes clear, she should be flogged (as the presribed) punishment, but hurl no reproach at her. If she commits adultery again, she should (again be punished) by flogging, but hurl no reproach upon her. It she commits fornication for the third time. and it becomes clear, then he should sell her, even if only for a rope of hair.
وَحَدَّثَنِي عِيسَى بْنُ حَمَّادٍ الْمِصْرِيُّ، أَخْبَرَنَا اللَّيْثُ، عَنْ سَعِيدِ بْنِ أَبِي سَعِيدٍ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّهُ سَمِعَهُ يَقُولُ سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ " إِذَا زَنَتْ أَمَةُ أَحَدِكُمْ فَتَبَيَّنَ زِنَاهَا فَلْيَجْلِدْهَا الْحَدَّ وَلاَ يُثَرِّبْ عَلَيْهَا ثُمَّ إِنْ زَنَتْ فَلْيَجْلِدْهَا الْحَدَّ وَلاَ يُثَرِّبْ عَلَيْهَا ثُمَّ إِنْ زَنَتِ الثَّالِثَةَ فَتَبَيَّنَ زِنَاهَا فَلْيَبِعْهَا وَلَوْ بِحَبْلٍ مِنْ شَعَرٍ " .