Muwatta Imam Malik Book of Hudud, Hadith 13

Malik related to me from Nafi that Safiyya bint Abi Ubayd informed him that a man who had had intercourse with a virgin slave- girl and made her pregnant was brought to Abu Bakr as-Siddiq. He confessed to fornication, and he was not muhsan. Abu Bakr gave the order and he was flogged with the hadd punishment. Then he was banished to Fadak, (thirty miles from Madina).
Malik spoke about a person who confessed to fornication and then retracted it and said, "I didn't do it. I said that for such-and-such a reason," and he mentioned the reason. Malik said, "That is accepted from him and the hadd is not imposed on him. That is because the hadd is what is for Allah, and it is only applied by one of two means, either by a clear proof which establishes guilt or by a confession which is persisted in so that the hadd is imposed. If someone persists in his confession, the hadd is imposed on him."
Malik said, "I have not seen the people of knowledge exiling slaves who have committed adultery."

حَدَّثَنِي مَالِكٌ، عَنْ نَافِعٍ، أَنَّ صَفِيَّةَ بِنْتَ أَبِي عُبَيْدٍ، أَخْبَرَتْهُ أَنَّ أَبَا بَكْرٍ الصِّدِّيقَ أُتِيَ بِرَجُلٍ قَدْ وَقَعَ عَلَى جَارِيَةٍ بِكْرٍ فَأَحْبَلَهَا ثُمَّ اعْتَرَفَ عَلَى نَفْسِهِ بِالزِّنَا وَلَمْ يَكُنْ أَحْصَنَ فَأَمَرَ بِهِ أَبُو بَكْرٍ فَجُلِدَ الْحَدَّ ثُمَّ نُفِيَ إِلَى فَدَكَ .