The Book of Financial Transactions
44/78. Chapter:
If there Is an invalid condition in a transaction, the transaction Is valid but that condition is invalid
Sunan an-Nasai
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 " .
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."
Reference : Sunan an-Nasa'i 4644In-book reference : Book 44, Hadith 196English translation : Vol. 5, Book 44, Hadith 4648