Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrates that when the Messenger of Allah (peace and blessings be upon him) sent Sayyiduna Mu’adh bin Jabal (may Allah be pleased with him) towards Yemen, he said to him:“You are going to a people from among the People of the Book. First, invite them to testify that there is no deity worthy of worship except Allah and that I am the Messenger of Allah. If they accept this from you, then inform them that Allah has made five prayers obligatory upon them during the day and night. If they accept this from you, then inform them that Allah has also made zakat obligatory upon their wealth, to be taken from their rich and distributed among their poor. If they accept this from you, then (when taking zakat) avoid taking their most valuable possessions, and beware of the supplication of the oppressed, for there is no barrier between it and Allah.”