Sunan An-Nasai, Chapter: The Book of the Times (of Prayer)

"We stayed in the Masjid one night waiting for the Messenger of Allah (saw) to pray Isha. He came out to us when one-third of the night or more had passed, and he said when he came out: 'You are waiting for a prayer for which the followers of no other religion are waiting. Were it not that I would impose too much difficulty on my Ummah, I would have led them in the prayer at this time.' Then he commanded the Muadhdhin to say the Iqamah and he prayed."