the Prophet send Muadh to Yemen, and said: “You are going to some people among the People of the Book. Call them to bear witness that none has the right to be worshipped but Allah, and that I am the messenger of Allah. If they obey that, then tell them that Allah has enjoined upon them five prayers every day and night. If they obey that, then tell them that Allah has enjoined upon them charity (Zakat) from their wealth, to be taken from the rich and given to their poor. If they obey that, then beware of (taking) the best of their wealth. And beware of the supplication of the oppressed, for there is no barrier between and Allah.”