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