Abu Sa’eed al-Khudri may Allah be pleased with him, said: “I heard the Prophet saying: “Indeed, anyone who fasts for one day for Allah's pleasure, Allah will keep his face away from the Hellfire for (a distance covered by a journey of) seventy years.””[Al-Bukhari & Muslim]
Abu Hurayrah may Allah be pleased with him, reported that the Messenger of Allah said: “Allah the Exalted and Majestic says: ‘Every act of the son of Adam is for him, except fasting. It is (exclusively) meant for Me and I (alone) will reward it.’ Fasting is a shield (i.e. it protects one from the Fire and from his desires). When any one of you is fasting, he should neither indulge in obscene language, nor raise his voice. If anyone reviles him or tries to quarrel with him, he should say: I am a fasting person. By Him in whose Hand is the life of Muhammad, the breath of the observer of a fast is sweeter to Allah on the Day of Judgment than the fragrance of musk. The one who fasts has two (occasions) of joy, one when he breaks the fast and is delighted by the breaking of (the fast), and one when he meets his Lord and is delighted with his fast.”[Al-Bukhari & Muslim]
Al-Waqqaadi said: “Imaam Ibn Abu Thi’b would pray the entire night and exert great efforts in worship. If he were to have been told that the next day was the Day of Judgment, he could not have done more than what he was already doing. His brother told me that he would fast every other day, and at the end of his life, he would fast daily.”
Muhammad ibn Abdul-A’laa said: “Mu’tamir ibn Sulaymaan told me: ‘For forty years, my father used to fast every other day and would pray the Fajr prayer with the same ablution of that of the ‘Ishaa’ prayer (i.e. he would pray the entire night).’”
A group of scholars who taught Qazween said about him: “He fasted for thirty years without missing a day, and when it was time to break his fast at sunset, he would do so eating bread and salt. His virtues were more than could be enumerated.”
‘Atiyyah ibn Qays said: “A group of people from Damascus met Abu Muslim while he was fighting against the Romans. He had dug a hole inside his tent and placed water in it in order to cool himself whilst fasting. They said to him: ‘You are traveling, why are you fasting?’ he replied: ‘When the time for the actual fight comes, I will eat. I am preparing myself for the coming days (i.e. the Hereafter)’ ”
Ibn Abu ‘Uday said: “Daawood ibn Abu Hind fasted for forty years without his household members knowing about it. He would take his lunch with him when he left his house and would give it out in charity on the way. He would return home at sunset to eat with his family without them knowing what he had done.” Commenting on this story, Imaam Ibn Al-Jawzi said: “The people in the market would think that he would eat at home, and his family would think that he would eat at his shop.”
A man asked Ma’roof Al-Karkhi about the way he fasted. He interrupted him saying: “Our Prophet used to fast in such and such a manner, and Prophet Daawood, may Allah exalt his mention, would fast in such and such a manner.” However, the man insisted on knowing, so he said: “Every day, I start the day fasting, but if someone were to invite me to eat, I would accept his offer without telling him that I was fasting.”
The scholars of biography said that Nafeesah bint Al-Hasan used to fast very often. People advised her to give herself a break from fasting for some time, to which she replied: “How can I give myself a break when I have a huge obstacle ahead of me (i.e. the Day of Account) which only the devout would be able to overcome?” On the day she died, she was fasting, and when people tried to force her to break her fast, she said: “I have been asking Allah for the past thirty years to take my soul while I am fasting, and you want me now to break my fast? This will simply not happen!” She died whilst fasting, just as she had wished.