Sahih Muslim Book 5, Hadith Number 2206.
Chapter : Acceptance of Sadaqa by honest work and its growth.
Haritha b. Wahb reported Allah’s Messenger (may peace be upon him) as saying: Give Sadaqa for a time is about to come when a person would walk with alms and the one whom it is to be given would say: Had you brought it yesterday, I would have accepted it. For the present I do not need it. (And the giver of Sadaqa) I would not find anyone to accept it.