Sahih Bukhari Volume 002, Book 024, Hadith Number 515.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 24. Obligatory Charity Tax (Zakat)
Narated By Asma' bint Abu Bakr : That she had gone to the Prophet and he said, "Do not shut your money bag; otherwise Allah too will with-hold His blessings from you. Spend (in Allah's Cause) as much as you can afford. "