What is the limit for the preferred time of the Isha' prayer?
Chapter on Prayer Times
Al-Mughni
Book of Prayer
Primary text
The preferred time for Isha' prayer extends until one-third of the night, which is the ruling explicitly stated by Ahmad, 'Umar ibn Al-Khattab, Abu Hurairah, and Malik, supported by the narration of Jibreel's instruction to the Prophet (peace be upon him) on the second day regarding the time span between the two prayers.
Supporting text
Another opinion states that the end of the preferred time for Isha' is half the night, based on narrations from Anas ibn Malik and Abu Sa'id Al-Khudri. The ruling is that delaying beyond one-third of the night is permissible out of necessity up to half the night; anything beyond half the night is considered the time of necessity, similar to the situation for the Asr prayer.