Musannaf Ibn Abi Shayba 13:2198

Abu Bakr narrated to us, he said: Abd al-Wahhab al-Thaqafi narrated to us, from Ayyub, from Muhammad, that a man made a *kitabah* (contract of manumission) with a slave of his, and he stipulated his *wala* (patronage), his inheritance, and his house. When he paid his *kitabah*, he was emancipated after a time. Then his (the former master's) heirs disputed regarding his inheritance. Shurayh invalidated that. The master said: "What use is my condition to me [which I made] twenty years ago?" Shurayh said: "The condition of Allah [takes precedence] over your condition [which was made] fifty years ago."