The Messenger of Allah ﷺ was asked about a slave-woman who commits fornication, and she is not married: If she commits fornication, flog her: if she commits fornication again flog her; if only for a rope of hair (dafir). Ibn Shihab: I do not know whether he (the Prophet) said it is a third or a fourth time.  

أَنَّ رَسُولَ اللَّهِ ﷺ سُئِلَ عَنِ الأَمَةِ إِذَا زَنَتْ وَلَمْ تُحْصَنْ قَالَ إِنْ زَنَتْ فَاجْلِدُوهَا ثُمَّ إِنْ زَنَتْ فَاجْلِدُوهَا ثُمَّ إِنْ زَنَتْ فَاجْلِدُوهَا ثُمَّ إِنْ زَنَتْ فَبِيعُوهَا وَلَوْ بِضَفِيرٍ قَالَ ابْنُ شِهَابٍ لاَ أَدْرِي فِي الثَّالِثَةِ أَوِ الرَّابِعَةِ وَالضَّفِيرُ الْحَبْلُ  

When the slave-woman of any of you commits fornication, he should inflict the prescribed punishment on her, but not hurl reproaches at her. This is to be done up to three times. If she a fourth time, he should flog her, and sell her even if only for a rope of hair.  

عَنِ النَّبِيِّ ﷺ قَالَ إِذَا زَنَتْ أَمَةُ أَحَدِكُمْ فَلْيَحُدَّهَا وَلاَ يُعَيِّرْهَا ثَلاَثَ مِرَارٍ فَإِنْ عَادَتْ فِي الرَّابِعَةِ فَلْيَجْلِدْهَا وَلْيَبِعْهَا بِضَفِيرٍ أَوْ بِحَبْلٍ مِنْ شَعْرٍ  

He said each time: He should give her the appropriate beating according to Allah’s Book, but not Hurl reproaches at her. He said a fourth time: If she does it again, he should give her the appropriate beating according to Allah’s Book, and then should sell her even if only for a rope of hair.  

عَنِ النَّبِيِّ ﷺ بِهَذَا الْحَدِيثِ قَالَ فِي كُلِّ مَرَّةٍ فَلْيَضْرِبْهَا كِتَابُ اللَّهِ وَلاَ يُثَرِّبْ عَلَيْهَا وَقَالَ فِي الرَّابِعَةِ فَإِنْ عَادَتْ فَلْيَضْرِبْهَا كِتَابُ اللَّهِ ثُمَّ لْيَبِعْهَا وَلَوْ بِحَبْلٍ مِنْ شَعْرٍ