Muslims pray 5 times a day facing Mecca, with the Koran as their holy book. They are expected to make a pilgrimage to Mecca at least once in their life if able. With over 1 billion followers, they slaughter animals and dress modestly, and women may cover their heads and faces. Their holy day is Friday, and prayers involve cleaning body parts before praying on mats led by an imam, with men and women sitting separately.