Given the following passage  "Belief is a fundamental aspect of morality in the Quran, and scholars have tried to determine the semantic contents of "belief" and "believer" in the Quran. The ethico-legal concepts and exhortations dealing with righteous conduct are linked to a profound awareness of God, thereby emphasizing the importance of faith, accountability, and the belief in each human's ultimate encounter with God. People are invited to perform acts of charity, especially for the needy. Believers who "spend of their wealth by night and by day, in secret and in public" are promised that they "shall have their reward with their Lord; on them shall be no fear, nor shall they grieve". It also affirms family life by legislating on matters of marriage, divorce, and inheritance. A number of practices, such as usury and gambling, are prohibited. The Quran is one of the fundamental sources of Islamic law (sharia). Some formal religious practices receive significant attention in the Quran including the formal prayers (salat) and fasting in the month of Ramadan. As for the manner in which the prayer is to be conducted, the Quran refers to prostration. The term for charity, zakat, literally means purification. Charity, according to the Quran, is a means of self-purification.",  answer the following question. Note that the answer is present within the text.  Question: __ is a religious obligation for all Muslims who meet the necessary criteria of wealth
The answer to this question is:
zakat