The Book of Prayers (Kitab Al-Salat)
Muslim :: Book 4 : Hadith 1344
Ibn 'Umar said: The Messenger of Allah (may peace be upon him) said: Let the bedouin not gain upper band over you In regard to the name of your prayer, i. e. night prayer, for it is mentioned 'Isya' in the Book of Allah (i. e. the Qur'an). (The bedouin call it 'Atama because) they make delay in milling their she-camels.