Abu Hurairah (May Allah be pleased with him) said:
There came a man to the Prophet (ﷺ) and said, "O Messenger of Allah, which charity is the most rewardable?" He (ﷺ) said, "That you should give charity (in a state when you are) healthy and stingy and fear 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 be saying: 'This is for so-and-so, and this for so-and-so.' Lo! It has already come into (the possession of) so-and- so".[Al-Bukhari and Muslim].
Arabic/English book reference: Book 1, Hadith 90