The Virtues of fasting: The reward of fasting in summer is irrigation and watering on the Day of Thirst

Al Bazzar reported on the authority of Ibn `Abbas (may Allah be pleased with him) that the Messenger of Allah (peace be upon him) sent Abu Musa as a leader of a military detachment in the sea. When the detachment raised the sail in a dark night, a person cried saying: O people of the ship, shall I tell you about a promise made by Allah the Almighty? Abu Musa said: Tell us. He said: Indeed, Allah (Blessed and Exalted be He) promised the one who fasts and suffers thirst in a sunny day to quench his thirst on the Day of Thirst i.e., the Day of Judgment. In another narration: "Verily, Allah promised those who fast on a hot day to water them on the Day of Recompense. Therefore, Abu Musa used to seek the very hot day which a person could not stand to fast." [Al Albany graded it as good in Sahih Al Targhib: 1/412].

So, fasting summer days is one of the qualities of faith because of the length of summer days and their hot air. Ibn Rajab (may Allah bestow mercy on his soul) reported from some Predecessors their saying: "We were informed that the fasting people will have a banquet to eat from while people are still being reckoned. People will say: O Lord, we are being reckoned while they are eating! Thereupon, it will be said to them: They used to fast while you are not and stay up for worship while you were sleeping.

The people will not weep out of regret for something at their death more than the hot days in which they did not observe fasting.

Mu`adh ibn Jabal (may Allah be pleased with him) said at his death as was reported in Hilyat Al Awliya' and the book of Adh-Dhuhd of Imam Ahmad: "Welcome to death, a close visitor who came in a time of need. O Allah, I used to fear You, but today I hope for Your Mercy. O Allah, You know that I did not like the world for the flow of rivers or planting trees, but for fasting in hot days, worshiping for long hours, and accompanying scholars in knowledge sessions."