Sayyidina ibn Abbas (RA) reported that Allah’s Messenger (SAW) sent Mu’adh to Yemen. He instructed him : You will come to a people who are ot the scripture, so invite them to bear witness that there is no God but Allah and that I am Allah’s Messenger (SAW). If they submit to that inform them that Allah has made obligatory for them the five prayers during day and night. If they obey that then inform them that Allah has prescribed on them sadaqah on their wealth to be acquired from their wealthy and paid to their poor. If they submit to that then refrain from taking the best portion of their property as zakah. And, fear the supplication of the wronged one, for there is not any veil between the petition and Allah.
[Ahmed 2071,B740,Muslim 19,Abu Dawud 1584,Nisai 2434, Ibn e Majah783]