Sahih Al Bukhari – Book of Beginning Of Creation
Volumn 004, Book 054, Hadith Number 479.
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Narated By Sahl bin Sad RA : The Prophet PBUH said, "Paradise has eight gates, and one of them is called Ar-Raiyan through which none will enter but those who observe fasting." The Prophet also said, "If a person spends two different kinds of something (for Allah's Cause), he will be called from the gates of Paradise."