John Chrysostom

"Then, while the bridegroom tarried, they all slumbered and slept." He shows that the time intervening will not be short, leading His disciples away from the expectation that His kingdom was quite immediately to appear. For this indeed they hoped, therefore He is continually holding them back from this hope. And at the same time He intimates this too, that death is a sleep. For they slept, He saith.

Homily on the Gospel of Matthew 78 ↗

Theophylact of Ohrid

"Slumber" here means death, and the tarrying of the bridegroom means that the second coming does not occur immediately.

Commentary on Matthew ↗

Augustine of Hippo

But he tarried. And "while he tarried, they all slept." What is "all"? Both the foolish and the wise. "All slumbered and slept." But is this sleeping good? What does this sleep mean at this time? Might it mean that during the delay of the bridegroom there is an inattentiveness, so that "because of the increase of lawlessness, the love of many will grow cold"? Are we to understand this sleep in this way? I don't like that reading, and I will tell you why. Because among the ten are the five wise virgins. …

Sermon 93.5 ↗

Jerome

And while the bridegroom delayed, they all slumbered and slept. For not a little time passes between the first and second coming of the Lord. They all slumbered, that is, they died, because the death of the saints is called sleep. Moreover, it is said that they slept, because they will be raised afterwards.

Commentary on Matthew ↗

Gregory the Dialogist

"While the bridegroom tarried, they all slumbered and slept," because while the Judge delays His coming to the final judgment, both the elect and the reprobate are lulled in the sleep of death. For to sleep is to die. But to slumber before sleep is to languish from health before death, because through the weight of illness one arrives at the sleep of death.

Forty Gospel Homilies, Homily 12 ↗