Sa’eed ibn Yasar said that he heard Sayyidina Abu Hurayrah (RA) say that Allah’s Messeger said, “If anyone gives zakah from his lawful wealth—and Allah does not accept but the lawful—then the Compassionate takes it in His right hand even if it is a piece of date. Then it grows in the Hand of the Compassionate till it is bigger than a thountain. It is as though a person nourishes a colt or a calf.”
[Ahmed 10940, Bukhari 1410, Muslim 1014, Nisai 2521, Ibn e Majah 1842]