Sahih Muslim Book 5, Hadith Number 2250.

Chapter : Concerning the statement that the upper hand is better than the lower hand, and the upper hand is that which gives and the lower one is that which receives.

Abu Huraira reported that there came a person to the Messenger of Allah (may peace be upon him) and said: Messenger of Allah, which charity is the best? Upon this he said: That you should give charity (in a state when you are) healthy and close-fisted, one haunted by the fear of poverty, hoping to become rich (charity in such a state of health and mind is the best). And you must not defer (charity to such a length) that you are about to die and would he saying: This is for so and so, and this is for so and so. Lo, it has already come into (the possession of so and so).