Riyad as-Salihin 208
Mu'adh (May Allah bepleased with him) reported that Messenger of Allah (ﷺ) sent me (as a governor of Yemen) and instructed me thus:
"You will go to the people of the Book. First call them to testify that 'there is no true god except Allah, that I am (Muhammad (ﷺ)) the Messenger of Allah.' If they obey you, tell them that Allah has enjoined upon them five Salat (prayers) during the day and night; and if they obey you, inform them that Allah has made Zakat obligatory upon them; that it should be collected from their rich and distributed among their poor; and if they obey you refrain from picking up (as a share of Zakat) the best of their wealth. Beware of the supplication of the oppressed, for there is no barrier between it and Allah". [Al-Bukhari and Muslim] .
وعن معاذ رضي الله عنه قال ‏:‏ بعثني رسول الله صلى الله عليه وسلم فقال‏:‏ ‏
"‏إنك تأتي قومًا من أهل الكتاب، فادعهم إلى شهادة أن لا إله إلا الله، وأني رسول الله ، فإن هم أطاعوا لذلك، فأعلمهم أن الله قد افترض عليهم خمس صلوات في كل يوم وليلة، فإن هم أطاعوا لذلك، فإياك وكرائم أموالهم‏.‏ واتق دعوة المظلوم فإنه ليس بينها وبين الله حجاب‏"‏ ‏(‏‏(‏متفق عليه‏)‏‏)‏ ‏.‏