Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrates: When the Prophet Muhammad (peace and blessings be upon him) sent Sayyiduna Mu’adh (may Allah be pleased with him) to Yemen, he said:“You are going to a people from among the People of the Book, so first invite them to the worship of Allah. When they come to know Allah, then inform them that Allah has made five prayers obligatory upon them in every day and night. When they do this, then inform them that Allah has made zakat obligatory upon them, which will be taken from their wealth and returned to their poor. When they obey this, then take zakat from them, but avoid taking the best of people’s wealth.”

(Imam Ibn Hibban, may Allah have mercy on him, says:) This category, such as Hajj and Zakat and other similar obligations, are those which are made obligatory upon some sane and mature people in certain specific circumstances; they are not obligatory in every situation (i.e., zakat is obligatory upon the one who possesses the nisab and a year passes over it, and Hajj is obligatory upon the one for whom it is possible to reach Makkah during the specific days of Hajj. These are not obligatory upon every Muslim in every situation.)