"The Prophet (ﷺ) delayed 'Isha' one night until part of the night had passed. Then 'Umar, may Allah be pleased with him, got up and called out: 'The prayer, O Messenger of Allah! The women and children have gone to sleep.' Then the Messenger of Allah (ﷺ) came out with water dripping from his head, saying: 'This is (the best) time (for 'Isha'), were it not that this would be too difficult for my Ummah.'"
Sunan an-Nasa'i Book 6, Hadith 39
← Previous Hadith "I said to 'Ata': 'What is the best time you think I should pray Al-'Atamah, either in congregation or on my own?' He said: 'I heard Ibn 'Abbas say: "The Messenger of Allah (ﷺ) delayed Al-'Atamah one night until the people had slept and woken up, then slept and woken up again. Then 'Umar got up and said: 'The prayer, the prayer!'" 'Ata' said: 'Ibn 'Abbas said: "The Messenger of Allah (ﷺ) came out, and it is as if I can see him now, with water dripping from his head, putting his hand on the side of his head. .'" I checked with 'Ata' how the Prophet (ﷺ) put his hand on his head, and he showed me the same way as Ibn 'Abbas had done. 'Ata' spread his fingers a little, then placed them with the tips of his fingers on his forehead, then he drew his fingers together on his head until his thumb touched the edge of the ear that is next to the face, then moved it to his temple and forehead, then he said: 'Were it not that I would impose too much difficulty for my Ummah, I would have commanded them to offer this prayer only at this time.'"

Sunan an-Nasa'i Book 6, Hadith 38 Next Hadith → "The Messenger of Allah (ﷺ) used to delay the later 'Isha'."

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.

Sunan an-Nasa'i Book 6, Hadith 40