It was narrated that Ibn 'Umar said:
"The Messenger of Allah (ﷺ) said: 'Do not let the Bedouin make you change the name of this prayer of yours, for they delay the prayer until it is very dark because of their preoccupation with camels and milking them. Verily, it is 'Isha'.'"
English reference: Vol. 1, Book 6, Hadith 542
Arabic reference: Book 6, Hadith 546