Hadith: Which charity earns the greatest reward? He said: That you give charity when you are healthy and miserly, fearing poverty and hoping to become rich. Do not delay charity until your soul reaches up to the throat, and then you say: 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

عن أبي هريرة رضي الله عنه قال: جاء رجل إلى النبي صلى الله عليه وسلم فقال: يا رسول الله، أي الصدقة أعظم أجرًا؟ قال: «أن تَصَدَّقَ وأنت صحيحٌ شَحِيحٌ، تخشى الفقر وتَأَمَلُ الغِنى، ولا تُمْهِلْ حتى إذا بلغتِ الحُلْقُومَ قلت: لفلان كذا ولفلان كذا، وقد كان لفلان».
[صحيح] - [متفق عليه]

Abu Hurayrah (may Allah be pleased with him) reported that a man came to the Prophet (may Allah's peace and blessings be upon him) and said: "O Messenger of Allah, which charity earns the greatest reward?" He said: "That you give charity when you are healthy and miserly, fearing poverty and hoping to become rich. Do not delay (charity) until your soul reaches up to the throat and you then say: '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."
Sahih/Authentic. - [Al-Bukhari and Muslim]

Explanation

A man came to the Prophet (may Allah's peace and blessings be upon him) to ask him about the best type of charity. So he said to him: That you give charity when you are in good health and you fear poverty if you live long, and you hope to become rich. Do not defer charity until you are dying and you know that you are about to leave this world and then you say: "For so-and-so I give this amount of money as charity or as a bequest." Lo, the money then belongs to your heir, not to you.