Sahih Bukhari | Volume 9 | Hadith Number 345

Narrated by 'Ata
One night the Prophet delayed the 'Isha prayer whereupon 'Umar went to him and said, "The prayer, O Allah's Apostle! The women and children had slept." The Prophet came out with water dropping from his head, and said, "Were I not afraid that it would be hard for my followers (or for the people), I would order them to pray 'Isha prayer at this time." (Various versions of this Hadith are given by the narrators with slight differences in expression but not in content).