A man asked the Prophet (peace be upon him), "O Allah's Apostle! What kind of charity is the best?"
He (peace be upon him) replied. "To give in charity when you are healthy and greedy, hoping to be wealthy and afraid of becoming poor. Don't delay giving in charity till the time when you are on the death bed, when you say, 'Give so much to so-and-so and so much to so-and so,' and at that time the property is not (really) yours, but it belongs to so-and-so (i.e. your inheritors)."
Sahih Al-Bukhari Hadith 4.11 Narrated by Abu Huraira