Bukhari

Explanation:
The Companions (Sahabah) slept before the prayer due to delay. Thus, it is understood that at such a time, it is permissible to sleep before the ‘Isha prayer, provided that the ‘Isha prayer can still be performed in congregation. As is narrated here from the action of the Companions, this is the very purpose of the chapter.

The meaning of «لايقصر» is that just as I am passing my hand, in the same manner he passed his hand—not faster than this, nor slower than this. In some manuscripts, the word «لايعصر» appears, so the translation would be: neither wringing the hair nor grasping it in the hand, but rather doing it in this way; that is, pressing the hair with the fingers to extract the water.

Hadith Commentary:
(1)
In view of the narration of Ibn Umar (radi Allahu anhu), some scholars are of the opinion that ablution (wudu) is not nullified by sleep, because Ibn Umar (radi Allahu anhu) says that we slept in the mosque and there is no mention of performing ablution afterwards.
The answer to this is that it is possible they slept in such a manner, sitting firmly on the ground, that there was no possibility of passing wind, or that they lay down to sleep and, after waking up, performed ablution before joining the prayer.
Although the narration does not mention performing ablution, it was the habit of the noble Companions (radi Allahu anhum) that they would not perform prayer without ablution.
(Fath al-Bari: 2/67)
(2)
Imam Bukhari (rahimahullah), through both of the aforementioned narrations, has established that unintentional sleep before prayer is not disliked (makruh).
In cases of choice, it is disliked to sleep before the ‘Isha prayer at such a time when there is a risk of missing the prayer.
If someone has made arrangements to be awakened, then for him, sleeping before the prayer is in no way objectionable.
As Ibn Umar (radi Allahu anhu) would sometimes sleep before the ‘Isha prayer and instruct his family to wake him at the time of prayer.
The heading is established from the hadith of Ibn Abbas in this way: that the Messenger of Allah (sallallahu alayhi wa sallam), after coming to the mosque, did not object to those who were sleeping, rather, he praised their waiting.
It should be noted that while waiting for the Messenger of Allah (sallallahu alayhi wa sallam), some people returned to their homes, but ‘Uthman ibn Maz‘un (radi Allahu anhu) and about sixteen others remained in the mosque waiting for the Messenger of Allah (sallallahu alayhi wa sallam).
(Fath al-Bari: 2/68)