The scholars mention it is disliked due to the narration of the prophet صلى الله عليه و سلم regarding Isha:

كان يكره النوم قبلها و الحديث بعدها

“He used to dislike sleep before it and speech after it”

They said that:

• sleep before it because it may lead one to missing The Isha prayer in Jamaa’ah, and;
• speech after it because it may lead to him staying up all night and missing Fajr

And they mentioned other than this.

But they also mention that if one is in need of a short nap to give him strength to perform the Isha prayer and the likes, then they say it is  permissible due to the benefit that comes by it. But in this case, he should assign one to wake him up or set an alarm in Shaa Allaah

Translated by

Majid Jawed Al-Afghanee
Abu Layl