Abdullah bin Abbas reported,
Muaz reported that the Messenger of Allah ﷺ sent him to Yemen and said to him, "You are going to a people from the People of the Book. Call them to bear witness that there is no god but Allah and that I am the Messenger of Allah. If they obey you in that, then inform them that Allah has made five prayers obligatory upon them in every day and night. If they obey you in that, then inform them that Allah has made charity obligatory upon them, to be taken from their wealthy and returned to their poor. If they obey you in that, then beware of taking the choicest of their wealth, and beware of the supplication of the oppressed, for there is no barrier between it and Allah."
Azami 222
Sahihعن ابن عباس
أن معاذا قال: بعثني رسول الله ﷺ إلى اليمن، فقال: إنك تأتي قوما من أهل الكتاب، فادعهم إلى شهادة أن لا إله إلا الله، وأني رسول الله. فإن هم أطاعوا لذلك فأعلمهم أن الله افترض عليهم خمس صلوات في كل يوم وليلة، فإن هم أطاعوا لذلك فأعلمهم أن الله افترض عليهم صدقة تؤخذ من أغنيائهم فترد في فقرائهم، فإن هم أطاعوا لذلك فإياك وكرائم أموالهم، واتق دعوة المظلوم فإنه ليس بينها وبين الله حجاب.
Bukhari narrated it in the Book of Zakat (1496), and Muslim in the Book of Iman (19), both through Zakariya bin Ishaq, from Yahya bin Abdullah bin Sayfi, from Abu Mabad, the freedman of Ibn Abbas, from Ibn Abbas, who related it, and their wording is identical.Bukhari also narrated it (7372) from Abdullah bin Abu Aswad, who said, Fadl bin Ala told us, Ismail bin Umaya told us, from Yahya bin Abdullah bin Sayfi, that he heard Abu Mabad say, I heard Ibn Abbas say, "When the Prophet ﷺ sent Muaz toward Yemen, he said to him, 'You are going to a people among the People of the Book, so let the first thing you call them to be that they affirm the oneness of Allah Almighty.'" Then he related the rest of the hadith in the same way.In another version found in Bukhari (1458), it reads, "So let the first thing you call them to be the worship of Allah , and when they come to know Allah..."Both of them narrated it from a single teacher, namely Umaya bin Bistam Ayshi, from Yazid bin Zuray, from Rawh bin Qasim, from Ismail bin Umaya, with his chain of transmission, in the same manner.