Following astronomical calculations in acts of `Ibadah

Q 5: Is it permissible to follow the calculations of astronomers in the acts of `Ibadah (worship), such as Sawm (fasting) and others?

A: It is impermissible to follow astronomers in these matters; we should depend on sighting the new moon, as it is stated in the Sahih (authentic) Hadith, Observe Sawm when you see it (the crescent of Ramadan) and break your Sawm when you see it (the crescent of Shawwal). If the weather is cloudy, complete thirty days of Sha`ban. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.