533. Sunan an-Nasa’i Chapter: How Jibril Led The Prayer And The Definition Of The Times Of The Five Daily Prayers; Book 6, Hadith 40

[1] It is described as the later ‘Isha’ prayer because the Maghrib prayer is sometimes called ‘Isha’ prayer, but it is the first ‘Isha’. Some scholars are of the opinion that it is disliked to call Maghrib ‘Isha’ without qualifying it as the first ‘Isha’. See Fath Al-Bari.