The time of ´Isha´ prayer and delaying it

 ´Aishah narrated: The Prophet salla alayhi wa sallam one night delayed performing the ´Isha´ prayer until a great part of night passed and people in the mosque bad gone to sleep. He then came out and performed prayer and said: ´´This is the proper time for it; were it not for making it difficult for my Ummah.´´