Hadith
أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ عَمَّارٍ الْمَوْصِلِيُّ، عَنِ الْمُعَافَى، عَنْ زَكَرِيَّا بْنِ إِسْحَاقَ الْمَكِّيِّ، قَالَ حَدَّثَنَا يَحْيَى بْنُ عَبْدِ اللَّهِ بْنِ صَيْفِيٍّ، عَنْ أَبِي مَعْبَدٍ، عَنِ ابْنِ عَبَّاسٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم لِمُعَاذٍ حِينَ بَعَثَهُ إِلَى الْيَمَنِ " إِنَّكَ تَأْتِي قَوْمًا أَهْلَ كِتَابٍ فَإِذَا جِئْتَهُمْ فَادْعُهُمْ إِلَى أَنْ يَشْهَدُوا أَنْ لاَ إِلَهَ إِلاَّ اللَّهُ وَأَنَّ مُحَمَّدًا رَسُولُ اللَّهِ فَإِنْ هُمْ أَطَاعُوكَ بِذَلِكَ فَأَخْبِرْهُمْ أَنَّ اللَّهَ عَزَّ وَجَلَّ فَرَضَ عَلَيْهِمْ خَمْسَ صَلَوَاتٍ فِي يَوْمٍ وَلَيْلَةٍ فَإِنْ هُمْ - يَعْنِي أَطَاعُوكَ بِذَلِكَ - فَأَخْبِرْهُمْ أَنَّ اللَّهَ عَزَّ وَجَلَّ فَرَضَ عَلَيْهِمْ صَدَقَةً تُؤْخَذُ مِنْ أَغْنِيَائِهِمْ فَتُرَدُّ عَلَى فُقَرَائِهِمْ فَإِنْ هُمْ أَطَاعُوكَ بِذَلِكَ فَاتَّقِ دَعْوَةَ الْمَظْلُومِ " .
It was narrated that Ibn 'Abbas said:"The Messenger of Allah said to Mu'adh when he sent him to Yemen: 'You are going to some of the People of the book. When you come to them, call them to testify that there is none worthy of worship except Allah and that Muhammad is the Messenger of Allah. If they obey you in that, then tell them that Allah, the Mighty and Sublime, has enjoined on them a charity (Zakah) to be taken from their rich and given to their poor. If they obey you in that, then beware of the supplication of the oppressed person
Sahih · Abu Ghuddah
Sunan an-Nasa'i 2435 ·Book 23, Hadith 1·Also available on sunnah.com·