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. (Using translation from Abū Dāʾūd 4469)
أخْبَرَهُ أَنَّ رَسُولَ اللهِ ﷺ قَالَ لِلْوَلِيدَةِ إِنْ زَنَتْ فَاجْلِدُوهَا ثُمَّ إِنْ زَنَتْ فَاجْلِدُوهَا ثُمَّ إِنْ زَنَتْ فَاجْلِدُوهَا ثُمَّ إِنْ زَنَتْ فَبِيعُوهَا وَلَوْ بِضَفِيرٍ وَالضَّفِيرُ الْحَبْلُ فِي الثَّالِثَةِ أَوْ فِي الرَّابِعَةِ