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 لَمَّا بَعَثَ مُعَاذًا إِلَى الْيَمَنِ قَالَ «إِنَّكَ تَأْتِي قَوْمًا أَهْلَ كِتَابٍ فَادْعُهُمْ إِلَى أَنْ يَشْهَدُوا أَنْ لَا إِلَهَ إِلَّا اللَّهُ وَأَنَّ مُحَمَّدًا رَسُولُ اللَّهِ فَإِنْ أَطَاعُوا لَكَ فِي ذَلِكَ فَأَخْبِرْهُمْ أَنَّ اللَّهَ فَرَضَ عَلَيْهِمْ خَمْسَ صَلَوَاتٍ فِي كُلِّ يَوْمٍ وَلَيْلَةٍ فَإِنْ هُمْ أَطَاعُوا لَكَ فِي ذَلِكَ فَأَخْبِرْهُمْ أَنَّ اللَّهَ فَرَضَ عَلَيْهِمْ صَدَقَةً فِي أَمْوَالِهِمْ تُؤْخَذُ مِنْ أَغْنِيَائِهِمْ وَتُرَدُّ عَلَى فُقَرَائِهِمْ فَإِنْ هُمْ أَطَاعُوا لَكَ فِي ذَلِكَ فَإِيَّاكَ وَكَرَائِمَ أَمْوَالِهِمْ وَإِيَّاكَ وَدَعْوَةَ الْمَظْلُومِ فَإِنَّهُ لَيْسَ لَهَا مِنْ دُونِ اللَّهِ حِجَابٌ»