That the Messenger of Allah ﷺ forbade earnings of slave-girls.  

نَهَى رَسُولُ اللَّهِ ﷺ عَنْ كَسْبِ الإِمَاءِ  

Rafi' ibn Rifa'ah came to a meeting of the Ansar and said: The Prophet of Allah ﷺ forbade us (from some things) today, and he mentioned some things. He forbade the earning of a slave-girl except what she earned with her hand. He indicated (some things) with his fingers such as baking, spinning, and ginning.  

لَقَدْ نَهَانَا نَبِيُّ اللَّهِ ﷺ الْيَوْمَ فَذَكَرَ أَشْيَاءَ وَنَهَانَا عَنْ كَسْبِ الأَمَةِ إِلاَّ مَا عَمِلَتْ بِيَدِهَا وَقَالَ هَكَذَا بِأَصَابِعِهِ نَحْوَ الْخَبْزِ وَالْغَزْلِ وَالنَّفْشِ  

The Messenger of Allah ﷺ forbade earnings of a slave-girl unless it is known from where it came.  

نَهَى رَسُولُ اللَّهِ ﷺ عَنْ كَسْبِ الأَمَةِ حَتَّى يُعْلَمَ مِنْ أَيْنَ هُوَ