Sahih Bukhari Volume 001, Book 008, Hadith Number 446.
Narated By 'Aisha : Barira came to seek my help regarding her manumission. I told herself you like I would pay your price to your masters but your Al-Wala(1) would be for me." Her masters said, "If you like, you can pay what remains (of the price of her manumission), (Sufyan the sub-narrator once said), or if you like you can manumit her, but her (inheritance) Al-Wala would be for us. "When Allah's Apostle came, I spoke to him about it. He said, "Buy her and manumit her. No doubt Al-Wala(1) is for the manumitted." Then Allah's Apostle stood on the pulpit (or Allah's Apostle ascended the pulpit as Sufyan once said), and said, "What about some people who impose conditions which are not present in Allah's Book (Laws)? Whoever imposes conditions which are not in Allah's Book (Laws), his conditions will be invalid even if he imposed them a hundred times."