Ahmad ibn Muhammad from Musa ibn Al-Qasim from Ali ibn Ja'far from his brother (Imam) Musa ibn Ja'far عليه السلام, peace be upon them both, who said: I asked Him عليه السلام about an imam (of prayer) who recites a verse of prostration and then becomes impure (loses his ablution) before he performs the prostration, what should he do? Imam عليه السلام said: "He should appoint another person to lead; that person should perform the tashahhud, prostrate, and then they should all finish their prayer, and the Imam (of prayer) who became impure should withdraw, and the prayer of the congregation is complete."