Al-Matalib al-'Aliyah 1844 — The ruling on the apostate

Imam al-Humaydi narrated through Sufyan and Imran bin Zibyan from a man of Banu Hanifah, who said: Sayyiduna Abu Hurayrah (may Allah be pleased with him) asked me, "Do you know al-Rajjal (bin Unfuwah)?" I said, "Yes." He said, "Indeed, I heard the Messenger of Allah (peace and blessings be upon him) say, 'His (al-Rajjal's) molar tooth in the Fire will be bigger than (the mountain of) Uhud.'" The narrator said: That man had first accepted Islam, but later apostatised and joined Musaylimah the Liar, and he had said (out of tribal partisanship): "Two rams are butting each other, and the one dearer to me of the two is the one that wins, that is, my own ram (Musaylimah the Liar)."
This hadith describes the terrible end of this wretched man named al-Rajjal bin Unfuwah, who, despite having attained the company of the Prophet, sided with the trial of apostasy and affirmed the false prophethood of Musaylimah, as a result of which he was warned of the dreadful punishment of Hell.