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.
Sunan Abi Dawud Book 40, Hadith 119
← Previous Hadith A man came to the Prophet (ﷺ) and said: I contacted directly a women at the furthest part of the city (i.e., Medina), and I did with her everything except sexual intercourse. So here I am; inflict any punishment you wish. Thereupon ‘Umar said: Allah has concealed your fault; it would have been better if you also had concealed it yourself. The Prophet (ﷺ) sent a men after him. (When he came) he recited the verse: “And establish regular prayers at the two ends of the day and at the approaches of the night. . .” up to the end of the verse. A man from the people got up and asked: Is it particular to him, Messenger of Allah, or for the people in general? He replied: It is all the people.

Sunan Abi Dawud Book 40, Hadith 118 Next Hadith → 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.

Sunan Abi Dawud Book 40, Hadith 120