It is narrated from Sayyidah Aishah (may Allah be pleased with her) that one night the Messenger of Allah (peace and blessings be upon him) delayed the Isha prayer until much of the night had passed and the people of the mosque had fallen asleep. Then the Messenger of Allah (peace and blessings be upon him) went out to them and led them in prayer, and then said: "This is the best time for this prayer, were it not burdensome for my Ummah." These are the words of the hadith of Abd al-Razzaq; in the hadith of Hajjaj, which is reported from the Mother of the Believers Sayyidah Aishah (may Allah be pleased with her), he did not say the word "Isha", and the rest is the same.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2117