Al-Matalib al-'Aliyah 1001 — The virtue of fasting

It is narrated from Sayyiduna Sa'id bin Zayd bin Amr bin Nufayl (may Allah be pleased with him) that he said: I saw the Messenger of Allah (peace and blessings be upon him) turn towards Usamah bin Zayd (may Allah be pleased with them both) and say: "O Usamah, hold fast to the path of Paradise, and beware of being snatched away from the path before reaching it." He said: O Messenger of Allah, what is the deed by which this path is covered most swiftly? He (peace and blessings be upon him) said: "Enduring thirst in the scorching midday heat, and restraining the self from the pleasure (desire) of women. O Usamah, make fasting binding upon yourself, for it brings one near to Allah, the Mighty and Majestic. Indeed, nothing is more beloved to Allah Almighty than the smell of the mouth of the one who gave up food and drink purely for the sake of Allah. So if you are able to have death come to you while your stomach is hungry and your liver is thirsty, then do so, for by this deed you will attain a lofty rank in the Hereafter, and you will dwell in the company of the Prophets (peace be upon them); they will rejoice at the arrival of your soul, and the Almighty Compeller (al-Jabbar) will send down His mercy upon you." Then the narrator mentioned the complete hadith, in which are also these words: "O Usamah, know that the nearest of people to Allah Almighty on the Day of Resurrection will be those whose grief, thirst and hunger in this world lasted long."
In sha' Allah (if Allah wills), this report will come with all its details later in the Book of Zuhd (Asceticism).