The Book of Fasting (Kitab Al-Sawm)

Muslim :: Book 6 : Hadith 2369

'Abdullah b. Umar (Allah be pleased with both of them) reported Allah's Measenger (may peace be upon him) as saying: When you see the new moon, observe fast, and when you see it (again) then break it, and if the sky is cloudy for you, then calculate it.