Narrated Urwa:

Aisha told me that Buraira came to seek her help in writing for emancipation and at that time she had not paid any part of her price. 'Aisha said to her, "Go to your masters and if they agree that I will pay your price (and free you) on condition that your Wala' will be for me, I will pay the money." Buraira told her masters about that, but they refused, and said, "If 'Aisha wants to do a favor she could, but your Wala will be for us." Aisha informed Allah's Apostle of that and he said to her, "Buy and manumit Buraira as the Wala' will go to the manumitted."

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مَسْلَمَةَ، حَدَّثَنَا اللَّيْثُ، عَنِ ابْنِ شِهَابٍ، عَنْ عُرْوَةَ، أَنَّ عَائِشَةََ،ـ رضى الله عنها ـ أَخْبَرَتْهُ أَنَّ بَرِيرَةَ جَاءَتْ عَائِشَةَ تَسْتَعِينُهَا فِي كِتَابَتِهَا، وَلَمْ تَكُنْ قَضَتْ مِنْ كِتَابَتِهَا شَيْئًا، قَالَتْ لَهَا عَائِشَةُ ارْجِعِي إِلَى أَهْلِكِ، فَإِنْ أَحَبُّوا أَنْ أَقْضِيَ عَنْكِ كِتَابَتَكِ، وَيَكُونَ وَلاَؤُكِ لِي فَعَلْتُ. فَذَكَرَتْ ذَلِكَ بَرِيرَةُ إِلَى أَهْلِهَا فَأَبَوْا وَقَالُوا إِنْ شَاءَتْ أَنْ تَحْتَسِبَ عَلَيْكِ فَلْتَفْعَلْ، وَيَكُونَ لَنَا وَلاَؤُكِ. فَذَكَرَتْ ذَلِكَ لِرَسُولِ اللَّهِ ﷺ فَقَالَ لَهَا
" ابْتَاعِي فَأَعْتِقِي، فَإِنَّمَا الْوَلاَءُ لِمَنْ أَعْتَقَ ".