When Messenger of Allah ﷺ sent Muʿadh to Yemen, he said (to him), "YOU are going to people of a (Divine) Book. First of all invite them to worship Allah (alone) and when they come to know Allah, inform them that Allah has enjoined on them, five prayers in every day and night; and if they start offering these prayers, inform them that Allah has enjoined on them, the Zakat. And it is to be taken from the rich amongst them and given to the poor amongst them; and if they obey you in that, take Zakat from them and avoid (don't take) the best property of the people as Zakat."  

أَنَّ رَسُولَ اللَّهِ ﷺ لَمَّا بَعَثَ مُعَاذًا ؓ عَلَى الْيَمَنِ قَالَ إِنَّكَ تَقْدَمُ عَلَى قَوْمٍ أَهْلِ كِتَابٍ فَلْيَكُنْ أَوَّلَ مَا تَدْعُوهُمْ إِلَيْهِ عِبَادَةُ اللَّهِ فَإِذَا عَرَفُوا اللَّهَ فَأَخْبِرْهُمْ أَنَّ اللَّهَ قَدْ فَرَضَ عَلَيْهِمْ خَمْسَ صَلَوَاتٍ فِي يَوْمِهِمْ وَلَيْلَتِهِمْ فَإِذَا فَعَلُوا فَأَخْبِرْهُمْ أَنَّ اللَّهَ فَرَضَ عَلَيْهُمْ زَكَاةً {تُؤْخَذُ} مِنْ أَمْوَالِهِمْ وَتُرَدُّ عَلَى فُقَرَائِهِمْ فَإِذَا أَطَاعُوا بِهَا فَخُذْ مِنْهُمْ وَتَوَقَّ كَرَائِمَ أَمْوَالِ النَّاسِ