Under what conditions is delaying the Isha prayer recommended or disliked?
Chapter on Prayer Times
Al-Mughni
Book of Prayer
Primary text
Delaying the Isha prayer is recommended only for the individual worshipper or for a congregation that willingly accepts the delay. If there is hardship upon the congregation or some members thereof, delaying it is not recommended; rather, it becomes disliked (Makruh). The Prophet (peace be upon him) abandoned delaying the Isha and commanded against delaying it when it would cause hardship to his Ummah, based on the principle, "Whoever causes hardship to my Ummah, Allah will cause hardship to him." The Prophet (peace be upon him) only delayed it once or twice, likely due to being occupied or to reach the end of the time.
Supporting text
The Imam must follow the example of the Prophet (peace be upon him) by either praying early or delaying until others have gathered, or praying as was narrated by Al-Nu'man bin Bashir—when the moon had set for the third night—without imposing a delay that causes hardship on the worshippers. The Prophet (peace be upon him) commanded ease, stating, "I enter into prayer intending to prolong it, but hearing a child cry, I shorten it for fear of burdening its mother."