Sahih Muslim 1032 a
Abu Huraira reported that there came a person to the Messenger of Allah (ﷺ) 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).
حَدَّثَنَا زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا جَرِيرٌ، عَنْ عُمَارَةَ بْنِ الْقَعْقَاعِ، عَنْ أَبِي زُرْعَةَ، عَنْ أَبِي هُرَيْرَةَ، قَالَ أَتَى رَسُولَ اللَّهِ صلى الله عليه وسلم رَجُلٌ فَقَالَ يَا رَسُولَ اللَّهِ أَىُّ الصَّدَقَةِ أَعْظَمُ فَقَالَ ‏
"‏ أَنْ تَصَدَّقَ وَأَنْتَ صَحِيحٌ شَحِيحٌ تَخْشَى الْفَقْرَ وَتَأْمُلُ الْغِنَى وَلاَ تُمْهِلْ حَتَّى إِذَا بَلَغَتِ الْحُلْقُومَ قُلْتَ لِفُلاَنٍ كَذَا وَلِفُلاَنٍ كَذَا أَلاَ وَقَدْ كَانَ لِفُلاَنٍ ‏"‏ ‏.‏