Mishkat al-Masabih #1686

Ibn 'Abbas reported God's messenger as saying when he sent Mu'adh to the Yemen, “You will come to folk who are people of a book, so invite them to testify that there is no god but God and that Muhammad is God's messenger. If they obey that, tell them God has made obligatory for them five times of prayer every twenty-four hours. If they obey that, tell them God has made obligatory for them sadaqa to be taken from their rich and handed over to their poor. If they obey that, avoid taking the best parts of their property; and regard the claim of him who is wronged, for there is no veil between it and God." (Bukhari and Muslim.)