Zakāt, زكاة, "that which purifies" or "alms"), one of the Five Pillars of Islam, is the giving of a fixed portion of one's wealth to charity, generally to the poor and needy.
Zakat, a practice initiated by Muhammed himself, has played an important role throughout Islamic history. Initially, Muhammed instituted zakat as a voluntary, individual offering, but during his lifetime certain forms of zakat have been declared obligatory. The caliph Abū Bakr, believed by Sunni Muslims to be Muhammed's successor, was the first to institute a statutory zakat system. The third caliph, Uthman ibn Affan (who reigned from 644–656) significantly altered the zakat collection protocol, by decreeing that only "apparent" wealth was taxable, which had the effect of limiting zakat to mostly being paid on agricultural land and produce. Ultimately, the practice of state-administered zakat was very short-lived, ending with the reign of Umar bin Abdul Aziz from 717–720 A.D.