said When the Messenger of Allah ﷺ sent Mu’adh to Yemen, he said to him You are going to a people who are people of the book. So call them to bear witness that there is no diety but Allah, and that I am the Messenger of Allah. If they obey you in this respect, tell them that Allah has prescribed five prayers on them every day and night. If they obey you in this regard tell them that Allah has prescribed sadaqah(zakat) on their property and returned it to their poor. If they obey you in this respect, do not take the best of their property. Beware of the curse of the oppressed, for there is no curtain between it and Allah. (Using translation from Abū Dāʾūd 1584)  

أَنَّ النَّبِيَّ ﷺ بَعَثَ مُعَاذَ بْنَ جَبَلٍ إِلَى الْيَمَنِ فَقَالَ «إِنَّكَ تَأْتِي قَوْمَا أَهْلَ كِتَابٍ فَادْعُهُمْ إِلَى شَهَادَةِ أَنْ لَا إِلَهَ إِلَّا اللهُ وَأَنِّي رَسُولُ اللهِ فَإِنْ هُمْ أَطَاعُوا لَكَ فَأَعْلِمْهُمْ أَنَّ اللهَ افْتَرَضَ عَلَيْهِمْ خَمْسَ صَلَوَاتٍ فِي كُلِّ يَوْمٍ وَلَيْلَةٍ فَإِنْ هُمْ أَطَاعُوا لَكَ فَأَعْلِمْهُمْ أَنَّ اللهَ قَدِ افْتَرَضَ عَلَيْهِمْ صَدَقَةً فِي أَمْوَالِهِمْ تُؤْخَذُ مِنْ أَغْنِيَائِهِمْ وَتُرَدُّ فِي فُقَرَائِهِمْ فَإِنْ هُمْ أَطَاعُوكَ لِذَلِكَ فَإِيَّاكَ وَكَرَائِمَ أَمْوَالِهِمْ وَاتَّقِ دَعْوَةَ الْمَظْلُومِ فَإِنَّهَا لَيْسَ بَيْنَهَا وَبَيْنَ اللهِ حِجَابٌ»