It was narrated that 'Abdullah bin 'Amr said:"The Messenger of Allah said to me: 'Read the Qur'an in a month.' I said: 'I am able to do more than that. ' And I kept asking him until he said: 'In five days.' And he said: 'Fast three days a month.' I said: 'I am able to do more than that.' And 'Observe thhe most beloved of fasting to Allah, the Mighty and Sublime, the fast one day and not the next." (Suahih)

English translation · Sunan an-Nasa'i