“We used to sell our slave women and the mothers of our children (Umahat Awaldina) when the Prophet ﷺ was still living among us, and we did not see anything wrong with that.” (Using translation from Ibn Mājah 2517)   

أَنَّهُ سَمِعَ جَابِرَ بْنَ عَبْدِ اللَّهِ يَقُولُ «كُنَّا نَبِيعُ سَرَارِينَا أُمَّهَاتِ الْأَوْلَادِ وَالنَّبِيُّ ﷺ حَيٌّ فِينَا فَلَا يَرَى بِذَلِكَ بَأْسًا»  

We sold slave-mothers during the time of the Messenger of Allah ﷺ and of AbuBakr. When Umar was in power, he forbade us and we stopped. (Using translation from Abū Dāʾūd 3954)   

«كُنَّا نَبِيعُ أُمَّهَاتِ الْأَوْلَادِ عَلَى عَهْدِ رَسُولِ اللَّهِ ﷺ وَأَبِي بَكْرٍ فَلَمَّا كَانَ عُمَرُ نَهَى عَنْ بَيْعِهِنَّ»