Muhammad bin Isma'il bin Ibrahim محمد بن إسماعيل بن إبراهيم بن مقسم · The Book of Fasting

"We were forbidden in the Quran to ask the Prophet about anything not imperative, so we liked it when a wise man from among the people of the desert came and asked him. A man from among the desert people came and said: 'O Muhammad, your messenger came to us and told us that you say that Allah, the Mighty and Sublime, has sent you.' He said: 'He spoke the truth.' He said: 'Who created the heavens?' He said: 'Allah.'…

"I heard the Messenger of Allah say concerning Ramadan: 'Whoeve spends its nights in prayer (Qiyam) out of faith and in the hope of reward, he will be forgiven his previous sins." '

he asked the Messenger of Allah about fasting while traveling. He said: "If you wish to fast then fast, and if you wish not to fast then do not fast."

That they traveled with the Messenger of Allah. Some fasted and some did not, and those who were fasting did not criticize those who were not, and those who were not fasting did not criticize those who were.

"The Messenger of Allah entered my apartment and said: "I have been told that you stand all night (in prayer) and fast all day.' I said: 'Yes (I do).' He said: 'Do not do that. Sleep and stand (in prayer); fast and break your fast. For your eyes have a right over you, your body has a right over you, your body has a right over you, your wife has a right over you, your guest has a right over…

"I heard Abu Dharr, at Ar-Rabadhah, saying: 'The Messenger of Allah said: if you want to fast at any time during the monthm then fast on the thirteenth, fourteenth and fifteenth."'