Mukhtasar Bukhari

Narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Prophet Muhammad (peace and blessings be upon him) sent Sayyiduna Mu'adh (may Allah be pleased with him) as a judge to Yemen and said: "O Mu'adh! Encourage the people there to acknowledge that there is no deity except Allah and that I am the Messenger of Allah. If they accept this, then inform them that Allah has made five prayers obligatory upon them in every night and day. If they accept this as well, then inform them that Allah has made charity (zakat) obligatory upon their wealth, which will be taken from their rich and distributed among their poor."