Sahih Muslim Book 5, Hadith Number 2241.

Chapter : Exhortation to spend (for the sake of Allah) and disapproval of calculating (the articles of charity).

Abu Huraira reported Allah’s Messenger (may peace be upon him) as saying: He who spent pairs for the sake of Allah, the guardians of Paradise would call him, (in fact) every guardian of the door (of Paradise would welcome him saying): O, so and so, come on. Upon this Abu Bakr said: Messenger of Allah, (it means) there would be no distress on this person. The Messenger of Allah (may peace be upon him) said: I hope you would be among them.