When the Prophet (may Allah's peace and blessings be upon him) sent Mu‘ādh ibn Jabal (may Allah be pleased with him) to Yemen to call its people to Allah and teach them, he clarified to him that he would meet Christian people and that he should first call them to what is more important and then to what is less important, and so on. He should first call them to reform their creed by testifying that none is worthy of worship except Allah and that Muhammad is the Messenger of Allah. This is because they enter Islam with this testimony. If they complied with that, he should then enjoin them to establish the prayer, for it is the most important obligation after the testimony of Tawhīd (monotheistic belief). If they established the prayer, he should then order the rich amongst them to pay Zakah on their property to the poor amongst them. Thereafter, the Prophet (may Allah's peace and blessings be upon him) warned him not to take their best property; instead, it is required to adopt a moderate approach in this regard. Then, he (may Allah's peace and blessings be upon him) instructed him to avoid oppression, lest an oppressed person might supplicate to Allah against him, as his supplication is readily answered.