Sahih Bukhari, Chapter: Manumission of Slaves

that Barira came to seek her help in her writing of emancipation and she had to pay five Uqiya (of gold) by five yearly installments. Aisha said to her, "Do you think that if I pay the whole sum at once, your masters will sell you to me." Barira went to her masters and told them about the offer. They said that they would not agree to it unless her Wala would be for them. Aisha further said, "I went to Allah's Messenger (SAW) and told him about it." Allah's Messenger (SAW) said to her, "Buy Barira and manumit her and the Wala will be for the liberator." Allah's Messenger (SAW) the got up and said, "What about those people who stipulate that are not present in Allah's Laws? If anybody stipulates a condition which is not in Allah's Laws, then what he stipulates is invalid. Allah's Conditions (Laws) are the truth and are more solid."