It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that when the Noble Prophet, the Leader of both worlds, peace and blessings be upon him, sent Sayyiduna Mu’adh bin Jabal (may Allah be pleased with him) to Yemen, he said:“You are going to a people who are from the People of the Book. Invite them to bear witness that there is no deity except Allah and that I, Muhammad (peace and blessings be upon him), am the Messenger of Allah. If they obey you in this, then inform them that Allah has made five prayers obligatory upon them in every day and night. If they obey you in this as well, then inform them that Allah has made zakat obligatory upon their wealth, to be taken from their rich and distributed among their poor. If they accept this from you, then avoid taking the best of their wealth, and beware of the supplication of the oppressed, for there is no barrier between it and Allah.”