The command of Zakaat
Zakaat is an essential obligation among the obligations of Islam. This is the third article of Islam after the testification of the Unity of Allah Most High and the Prophethood of the Holy Prophet (Sallallahu alaihi wa sallam). Zakaat is obligatory on an adult, sane, free Muslim (man or woman) whose wealth reaches the prescribed limits as soon as a year passes on that wealth.
The person who denies the obligation of Zakaat is out of the fold of Islam. The past Ummah of different Prophets also had this obligation. For the Ummah of the Holy Prophet (Sallallahu alaihi wa sallam), this command was given in 2nd Hijri before fasts were made obligatory, when the condition of the Muslims was such that they badly needed mutual help and cooperation.
As given in Durre Mukhtaar, Kitab Uz Zakaat.