" I heard the Messenger of Allah say: 'The month is twenty-nine days."'
Sunan an-Nasa'i Book 22, Hadith 50
← Previous Hadith "The Messenger of Allah said: The month may be twenty-nine days or it may be thirty. When you see it, then stop fasting, and it is obscured from you (too cloudy), then complete the count."'

Sunan an-Nasa'i Book 22, Hadith 49 Next Hadith → "We are an unlettered Ummah, we do not use astronomical counting or computation. The month is like this, and this, and this," he did three times, showing it as twenty-nine.

Sunan an-Nasa'i Book 22, Hadith 51