Smak bin Hrb bin Aws سماك بن حرب بن أوس · The Book on Fasting

the Messenger of Allah said: "Do not fast before Ramadan. Fast with its sighting, and break fast with its sighting, and if it is obscured from you, then complete thirty days."

"A Bedouin came to the Prophet and said: 'I have seen the crescent.' So he said: 'Do you testify that none has the right to be worshipped but Allah? Do you testify that Muhammad is the Messenger of Allah?' He said: 'Yes.' So he said: 'O Bilal! Announce to the people that they should fast tomorrow.'"

"I was sitting with the Prophet when some drink was brought, so he drank from it, then he offered it to me and I drank it. Then I said: 'I have indeed sinned, so seek forgiveness for me.' He said: 'What is that?' I said: 'I was fasting, then I broke the fast.' He said: 'Were you performing a fast that you had to make up?' I said: 'No.' He said: 'Then it is no harm for you.'"

"The Messenger of Allah took a covenant from me for three: To not sleep except after performing Witr, to fast three days of every month, and to perform the Duha prayer."