Sahih Muslim 1705 a
Abd al-Rahman reported that 'Ali, while delivering the address said:
O people, impose the prescribed punishment upon your slaves, those who are married and those not married, for a slave-woman belonging to Allah's Messenger (ﷺ) had committed adultery, and he committed me to flog her. But she had recently given birth to a child and I was afraid that if I flogged her I might kill her. So I mentioned that to Allah's Apostle (ﷺ) and he said: You have done well.
حَدَّثَنَا مُحَمَّدُ بْنُ أَبِي بَكْرٍ الْمُقَدَّمِيُّ، حَدَّثَنَا سُلَيْمَانُ أَبُو دَاوُدَ، حَدَّثَنَا زَائِدَةُ، عَنِ السُّدِّيِّ، عَنْ سَعْدِ بْنِ عُبَيْدَةَ، عَنْ أَبِي عَبْدِ الرَّحْمَنِ، قَالَ خَطَبَ عَلِيٌّ فَقَالَ يَا أَيُّهَا النَّاسُ أَقِيمُوا عَلَى أَرِقَّائِكُمُ الْحَدَّ مَنْ أَحْصَنَ مِنْهُمْ وَمَنْ لَمْ يُحْصِنْ فَإِنَّ أَمَةً لِرَسُولِ اللَّهِ صلى الله عليه وسلم زَنَتْ فَأَمَرَنِي أَنْ أَجْلِدَهَا فَإِذَا هِيَ حَدِيثُ عَهْدٍ بِنِفَاسٍ فَخَشِيتُ إِنْ أَنَا جَلَدْتُهَا أَنْ أَقْتُلَهَا فَذَكَرْتُ ذَلِكَ لِلنَّبِيِّ صلى الله عليه وسلم فَقَالَ ‏
"‏ أَحْسَنْتَ ‏"‏ ‏.‏