Narrated Ibn Umar:

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 Allah's Apostle who said, "This (condition) should not prevent you from buying her, for the Wala is for the one who manumits (the slave)."

حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، عَنْ مَالِكٍ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، أَنَّ عَائِشَةَ أُمَّ الْمُؤْمِنِينَ، أَرَادَتْ أَنْ تَشْتَرِيَ جَارِيَةً تُعْتِقُهَا فَقَالَ أَهْلُهَا نَبِيعُكِهَا عَلَى أَنَّ وَلاَءَهَا لَنَا. فَذَكَرَتْ لِرَسُولِ اللَّهِ ﷺ فَقَالَ " لاَ يَمْنَعُكِ ذَلِكِ، فَإِنَّمَا الْوَلاَءُ لِمَنْ أَعْتَقَ ".