The Book Zakah and Fasting (Arousing the Intellects With an Explanation of Umdatul-Ahkaam )
Az-Zakah in the Shariah: An Obligatory portion of a particular wealth for a specific group or way. It was made mandatory in Mecca before the Hijrah and its obligations, portions, and receivers were clarified in Medinah. It is one of the Pillars of Islam, so if anyone denies its obligation then he is a disbeliever, because he has desbelieved in Allaah and His Messenger.
As-Siyaam (fasting) in the language means" Refraining from a thing. In the legislation it means refraining from food, drink and the rest of the nullifiers; from the appearance of the second fajr to the setting of the sun, in worship of Allaah, The Mighty and Majestic.
Allaah has obligated fasting upon His slaves within every religion. Allaah The Exhalted has said: O You who believe! Fasting has been prescribed for you as it was prescribed for those before you, that you may become pious.