(39) باب وَقْتِ الْعِشَاءِ وَتَأْخِيرِهَا
Ibn 'Umar said:
The Messenger of Allah (ﷺ) 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.
Reference: Sahih Muslim 644 b
In-book reference: Book 5, Hadith 292
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 1344