Narrated Abu Ma'bad,:

(the slave of Ibn Abbas) Allah's Apostle ﷺ said to Muadh when he sent him to Yemen, "You will go to the people of the Scripture. So, when you reach there, invite them to testify that none has the right to be worshipped but Allah, and that Muhammad is His Apostle. And if they obey you in that, tell them that Allah has enjoined on them five prayers in each day and night. And if they obey you in that tell them that Allah has made it obligatory on them to pay the Zakat which will be taken from the rich among them and given to the poor among them. If they obey you in that, then avoid taking the best of their possessions, and be afraid of the curse of an oppressed person because there is no screen between his invocation and Allah."

حَدَّثَنَا مُحَمَّدٌ، أَخْبَرَنَا عَبْدُ اللَّهِ، أَخْبَرَنَا زَكَرِيَّاءُ بْنُ إِسْحَاقَ، عَنْ يَحْيَى بْنِ عَبْدِ اللَّهِ بْنِ صَيْفِيٍّ، عَنْ أَبِي مَعْبَدٍ، مَوْلَى ابْنِ عَبَّاسٍ عَنِ ابْنِ عَبَّاسٍ ـ رضى الله عنهما ـ قَالَ قَالَ رَسُولُ اللَّهِ ﷺ لِمُعَاذِ بْنِ جَبَلٍ حِينَ بَعَثَهُ إِلَى الْيَمَنِ
" إِنَّكَ سَتَأْتِي قَوْمًا أَهْلَ كِتَابٍ، فَإِذَا جِئْتَهُمْ فَادْعُهُمْ إِلَى أَنْ يَشْهَدُوا أَنْ لاَ إِلَهَ إِلاَّ اللَّهُ وَأَنَّ مُحَمَّدًا رَسُولُ اللَّهِ، فَإِنْ هُمْ أَطَاعُوا لَكَ بِذَلِكَ، فَأَخْبِرْهُمْ أَنَّ اللَّهَ قَدْ فَرَضَ عَلَيْهِمْ خَمْسَ صَلَوَاتٍ فِي كُلِّ يَوْمٍ وَلَيْلَةٍ، فَإِنْ هُمْ أَطَاعُوا لَكَ بِذَلِكَ فَأَخْبِرْهُمْ أَنَّ اللَّهَ قَدْ فَرَضَ عَلَيْهِمْ صَدَقَةً تُؤْخَذُ مِنْ أَغْنِيَائِهِمْ فَتُرَدُّ عَلَى فُقَرَائِهِمْ، فَإِنْ هُمْ أَطَاعُوا لَكَ بِذَلِكَ فَإِيَّاكَ وَكَرَائِمَ أَمْوَالِهِمْ، وَاتَّقِ دَعْوَةَ الْمَظْلُومِ، فَإِنَّهُ لَيْسَ بَيْنَهُ وَبَيْنَ اللَّهِ حِجَابٌ ".