Sunan an-Nasa'i, Volume 5, Book 44, Hadith 4648 (DarusSalam) ⓘ

It was narrated from'Abdullah bin 'Umar that 'Aishah wanted to but a slave woman to set her free, but her people said: "We will sell her to you on condition that her loyalty (Walla) is to us," She mentioned that top the Messenger of Allah and he said: "That should not stop you. Loyalty belongs to the one who sets the slave free."

أَخْبَرَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، عَنْ مَالِكٍ، عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ عَائِشَةَ، أَرَادَتْ أَنْ تَشْتَرِيَ، جَارِيَةً تَعْتِقُهَا فَقَالَ أَهْلُهَا نَبِيعُكِهَا عَلَى أَنَّ الْوَلاَءَ لَنَا ‏.‏ فَذَكَرَتْ ذَلِكَ لِرَسُولِ اللَّهِ صلى الله عليه وسلم فَقَالَ ‏ "‏ لاَ يَمْنَعُكِ ذَلِكَ فَإِنَّ الْوَلاَءَ لِمَنْ أَعْتَقَ ‏" ‏ ‏.‏