Sahih al-Bukhari 2234
Narrated Abu Huraira:
I heard the Prophet (ﷺ) saying, "If a slave-girl of yours commits illegal sexual intercourse and her illegal 
sexual intercourse is proved, she should be lashed, and after that nobody should blame her, and if she 
commits illegal sexual intercourse the second time, she should be lashed and nobody should blame her 
after that, and if she does the offense for the third time and her illegal sexual intercourse is proved, she 
should be sold even for a hair rope."
حَدَّثَنَا عَبْدُ الْعَزِيزِ بْنُ عَبْدِ اللَّهِ، قَالَ أَخْبَرَنِي اللَّيْثُ، عَنْ سَعِيدٍ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ ـ رضى الله عنه ـ قَالَ سَمِعْتُ النَّبِيَّ صلى الله عليه وسلم يَقُولُ ‏
"‏ إِذَا زَنَتْ أَمَةُ أَحَدِكُمْ، فَتَبَيَّنَ زِنَاهَا فَلْيَجْلِدْهَا الْحَدَّ، وَلاَ يُثَرِّبْ عَلَيْهَا، ثُمَّ إِنْ زَنَتْ فَلْيَجْلِدْهَا الْحَدَّ وَلاَ يُثَرِّبْ، ثُمَّ إِنْ زَنَتِ الثَّالِثَةَ فَتَبَيَّنَ زِنَاهَا فَلْيَبِعْهَا وَلَوْ بِحَبْلٍ مِنْ شَعَرٍ ‏"‏‏.‏