Bayhaqi 21556 — The mudabbar may be sold whenever his owner wishes

Al-Shafi'i (may Allah have mercy on him) said: Someone said: We have narrated from Abu Ja'far Muhammad bin Ali that the Prophet (peace and blessings be upon him) sold only the service of the mudabbar. I said to him: "As far as I know, no one whose hadith is established has narrated this from Abu Ja'far; and even if someone whose hadith is established had narrated it, there would be no proof in it for you, for several reasons." He said: What are they? I said: "You do not accept a munqati' (broken) report as established even when nothing else contradicts it, so how can you accept as established a munqati' report that is contradicted by a connected, established one, if it does contradict it?" He said: Does it contradict it? I said: "It is not a (proper) hadith, that I should need to mention it." He said: Mention it according to what you hold about it. I said: "If it were established, it would be possible for me to say: The Prophet (peace and blessings be upon him) sold the person of a mudabbar, as Jabir narrated, and the service of a mudabbar, as Muhammad bin Ali narrated."
He spoke at length in answering it. Abd al-Ghaffar bin al-Qasim narrated it with a connected chain from Abu Ja'far, from Jabir, but Ali bin al-Madini used to accuse this Abd al-Ghaffar of fabrication. Abu Shaybah Ibrahim bin Uthman also narrated it with a connected chain from Uthman bin Umayr, from Abu Ja'far, from Jabir; but Abu Shaybah is da'if (weak), and the likes of him are not used as proof. Something similar to the narration of Ata, Amr and Abu al-Zubayr from Jabir has also been narrated from Mujahid and Muhammad bin al-Munkadir, from Jabir.