كتاب الزكاة
12  
The Book of Zakat
(31)
Chapter: The best of charity is that which is given when one is healthy and inclined to be stingy
(31)
باب بَيَانِ أَنَّ أَفْضَلَ الصَّدَقَةِ صَدَقَةُ الصَّحِيحِ الشَّحِيحِ ‏
Sahih Muslim 1032 b

Abu Huraira reported that a person came to the Messenger of Allah (ﷺ) and said:

Messenger of Allah, which charity is the greatest in reward? (The Prophet said): By your father, beware, you should give charity (in a state when you are) healthy and close-fisted, haunted by the fear of poverty, and still hoping to live (as rich). And you must not defer charity (to the time) when you are about to die, and would then say:" This is for so and so, and this for so and so." It has already become the possession of so and so.
وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، وَابْنُ، نُمَيْرٍ قَالاَ حَدَّثَنَا ابْنُ فُضَيْلٍ، عَنْ عُمَارَةَ، عَنْ أَبِي زُرْعَةَ، عَنْ أَبِي هُرَيْرَةَ، قَالَ جَاءَ رَجُلٌ إِلَى النَّبِيِّ صلى الله عليه وسلم فَقَالَ يَا رَسُولَ اللَّهِ أَىُّ الصَّدَقَةِ أَعْظَمُ أَجْرًا فَقَالَ ‏ "‏ أَمَا وَأَبِيكَ لَتُنَبَّأَنَّهُ أَنْ تَصَدَّقَ وَأَنْتَ صَحِيحٌ شَحِيحٌ تَخْشَى الْفَقْرَ وَتَأْمُلُ الْبَقَاءَ وَلاَ تُمْهِلْ حَتَّى إِذَا بَلَغَتِ الْحُلْقُومَ قُلْتَ لِفُلاَنٍ كَذَا وَلِفُلاَنٍ كَذَا وَقَدْ كَانَ لِفُلاَنٍ ‏"‏ ‏.‏
Reference : Sahih Muslim 1032b
In-book reference : Book 12, Hadith 120
USC-MSA web (English) reference : Book 5, Hadith 2251
  (deprecated numbering scheme)