Musannaf Ibn Abi Shayba 13:2247

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Sufyan narrated to us, from Abu Ja’far al-Farra’, from Abu Layla al-Kindi: That Salman wanted to enter into a *kitabah* (manumission contract) with a slave of his. He (Salman) said: "From where (will you get the money)?" He (the slave) said: "I will ask the people." He (Salman) said: "Do you want to feed me the filth of the people?" So he refused to enter into a *kitabah* with him.