George Leo Haydock

And while the bridegroom (Jesus Christ) tarried, i.e. delayed his coming, and thus protracted the time of repentance, they all slumbered and slept; viz. they all died. Hence St. Paul, nolo vos ignorare de dormientibus. But the reason why Jesus Christ says they slumbered is, because they were to rise again: and by the expression, whilst the bridegroom tarried, Christ wishes to shew us that a very short time will elapse between his first and second coming. (St. Jerome)