Bukayr bin 'Abdullah bin al-Ashj بكير بن عبد الله بن الأشج · The Book of Fasting

"(Allah says) fasting is for me and I shall reward for it. The fasting person rejoices twice: when he breaks his fast and the day when he meets his Lord. And the smell that come from the mouth of the fasting person is better before Allah than the fragrance of musk." '

"The Messenger of Allah went out to Makkah, and he fasted until he came to 'Usfan. Then he called for a cup and drank." (One of the narrators) Shubah said: "(That was) in Ramadan. Ibn 'Abbas used to say: 'Whoever wants to fast, may fast, and whoever wants to break may break his fast."'

That the Messenger of Allah fasted during Ramadan and broke his fast when traveling.

"We traveled with the Messenger of Allah and some of us fasted and some of us did not."