Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) bought a slave girl from his wife, and the wife set the condition that she would serve her. When Sayyiduna Umar (may Allah be pleased with him) was asked, he said: "Any wealth in which someone else has a right is not your wealth."
Hadith Referenceسنن سعید بن منصور / كتاب الطلاق / 3429
Hadith Gradingمحدثین:إسناده صحيح
Hadith Takhrij«إسناده صحيح، وأخرجه سعيد بن منصور فى «سننه» ترقيم الدرالسلفية برقم:، 2252، وابن أبى شيبة فى «مصنفه» برقم: 22169، والطبراني فى«الكبير» برقم: 9200»
Brief Explanation
Fiqhi Point: If something (a female or male slave) is sold and a condition is left remaining for someone else, for example: a condition of service, a condition of buying back, etc., then it completely negates ownership. Sayyiduna Umar radi Allahu anhu stated a golden principle: «لَيْسَمِنْمَالِكَمَاكَانَفِيهِشَرْطٌلِغَيْرِكَ» "That in which another has a conditional right is not counted as your property."