That Aisha, the mother of the Believers, intended to buy a slave girl in order to manumit her. The slave girl's master said, "We are ready to sell her to you on the condition that her Wala should be for us." Aisha mentioned that to Messenger of Allah ﷺ who said, "This (condition) should not prevent you from buying her, for the Wala is for the one who manumits (the slave)."  

أَهْلُهَا نَبِيعُكِهَا عَلَى أَنَّ وَلاَءَهَا لَنَا فَذَكَرَتْ لِرَسُولِ اللَّهِ ﷺ فَقَالَ لاَ يَمْنَعُكِ ذَلِكِ فَإِنَّمَا الْوَلاَءُ لِمَنْ أَعْتَقَ  

Aisha said, "I bought Barira and her masters stipulated that the Wala would be for them." Aisha mentioned that to the Prophet ﷺ and he said, "Manumit her, as the Wala is for the one who gives the silver (i.e. pays the price for freeing the slave)." Aisha added, "So I manumitted her. After that, the Prophet caller her (Barira) and gave her the choice to go back to her husband or not. She said, "If he gave me so much and so much (money) I would not stay with him." So she selected her ownself (i.e. refused to go back to her husband)."  

قَالَتِ اشْتَرَيْتُ بَرِيرَةَ فَاشْتَرَطَ أَهْلُهَا وَلاَءَهَا فَذَكَرَتْ ذَلِكَ لِلنَّبِيِّ ﷺ فَقَالَ أَعْتِقِيهَا فَإِنَّ الْوَلاَءَ لِمَنْ أَعْطَى الْوَرِقَ قَالَتْ فَأَعْتَقْتُهَا قَالَتْ فَدَعَاهَا رَسُولُ اللَّهِ ﷺ فَخَيَّرَهَا مِنْ زَوْجِهَا فَقَالَتْ لَوْ أَعْطَانِي كَذَا وَكَذَا مَا بِتُّ عِنْدَهُ فَاخْتَارَتْ نَفْسَهَا