Musannaf Ibn Abi Shayba 3:967

Hussain bin Ali narrated to us, from Za'idah, from Mansur, from al-Hakam, from Nafi', from Ibn Umar, who said: We waited one night for the Messenger of Allah (may Allah bless him and grant him peace) for the final night prayer (Isha) until it was a third of the night, or after that. Then he came out to us, and I do not know if something occupied him or a need he had regarding his family. He said: "I do not know of any people of a religion who wait for this prayer other than you. And were it not that it would be difficult for my nation, I would have prayed this prayer with them at this hour."