For He not only speaks to those in whose hearing He then spake, but even to all who came after them, before our time, and even to us, and to all after us, even to His last coming. but shall that day find all living, or will any man say that He speaks also to the dead, when He says, “Watch, lest when he cometh he find you sleeping?”
Why then does He say to all, what only belongs to those who shall then be alive, if it be not that it belongs to all, as I have said? For that day comes to each man when his day comes for departing from this life such as he is to be, when judged in that day, and for this reason every Christian ought to watch, lest the Advent of the Lord find him unprepared; but that day shall find him unprepared, whom the last day of his life shall find unprepared.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: Epist., 199, 3