The Necessity for Watchfulness
"But of that day or that hour no one knows, not even the angels in heaven, nor the Son, but only the Father. Take heed, watch and pray;[a] for you do not know when the time will come. It is like a man going on a journey, when he leaves home and puts his servants in charge, each with his work, and commands the doorkeeper to be on the watch. Watch therefore—for you do not know when the master of the house will come, in the evening, or at midnight, or at cockcrow, or in the morning - lest he come suddenly and find you asleep. And what I say to you I say to all: Watch."
Theophylact - The Lord wishing to prevent His disciples from asking about that day and hour, says, "But of that day and that hour knoweth no man, no, not the angels which are in heaven, neither the Son, but the Father."
For if He had said, I know, but I will not reveal it to you, He would have saddened them not a little; but He acted more wisely, and prevents their asking such a question, lest they should importune Him, by saying, neither the Angels, nor I.
Hilary, de Trin., ix - This ignorance of the day and hour is urged against the Only-Begotten God, as if, God born of God had not the same perfection of nature as God. But first, let common sense decide whether it is credible that He, who is the cause that all things are, and are to be, should be ignorant of any out of all these things. For how can it be beyond the knowledge of that nature, by which and in which that which is to be done is contained? And can He be ignorant of that day, which is the day of His own Advent? Human substances foreknow as far as they can what they intend to do, and the knowledge of what is to be done, follows upon the will to act. How then can the Lord of glory, from ignorance of the day of His coming, be believed to be of that imperfect nature, which has on it a necessity of coming, and has not attained to the knowledge of its own advent?
But again, how much more room for blasphemy will there be, if a feeling of envy is ascribed to God the Father, in that He has withheld the knowledge of His beatitude from Him to whom He gave a foreknowledge of His death. But if there are in Him all the treasures of knowledge, He is not ignorant of this day; rather we ought to remember that the treasures of wisdom in Him are hidden; His ignorance therefore must be connected with the hiding of the treasures of wisdom, which are in Him.
For in all cases, in which God declares Himself ignorant, He is not under the power of ignorance, but either it is not a fit time for speaking, or it is an economy of not acting.
But if God is said then to have known that Abraham loved Him, when He did not hide that His knowledge from Abraham, it follows, that the Father is said to know the day, because He did not hide it from the Son. If therefore the Son knew not the day, it is a Sacrament of His being silent, as on the contrary the Father alone is said to know, because He is not silent. But God forbid that any new and bodily changes should be ascribed to the Father or the Son.
Lastly, lest He should be said to be ignorant from weakness, He has immediately added, "Take ye heed, watch and pray, for ye know not when the time is."
Pseudo-Jerome - For we must needs watch with our souls before the death of the body.
Theophylact - But He teach us two things, watching and prayer; for many of us watch, but watch only to pass the night in wickedness; He now follows this up with a parable, saying, "For the Son of Man is as a man taking a far journey, who left his house, and gave his servants power over every work, and commanded the porter to watch."
Bede - The man who taking a far journey left his house is Christ, who ascending as a conqueror to His Father after the Resurrection, left His Church, as to His bodily presence, but has never deprived her of the safeguard of His Divine presence.
Greg, Hom in Evan, 9 - For the earth is properly the place for the flesh, which was as it were carried away to a far country, when it was placed by our Redeemer in the heavens. "And he gave his servants power over every work," when, by giving to His faithful ones the grace of the Holy Ghost, He gave them the power of serving every good work.
He has also ordered the porter to watch, because He commanded the order of pastors to have a care over the Church committed to them. Not only, however, those of us who rule over Churches, but all are required to watch the doors of their hearts, lest the evil suggestions of the devil enter into them, and lest our Lord find us sleeping.
Wherefore concluding this parable He adds, "Watch ye therefore: for ye know not when the master of the house cometh, at even, or at midnight, or at cockcrow, or in the morning: lest coming suddenly he find you sleeping."
Pseudo-Jerome - For he who sleeps applies not his mind to real bodies, but to phantoms, and when he awakes, he possesses not what he had seen; so also are those, whom the love of this world seizes upon in this life; they quit after this life what they dreamed was real.
Theophylact - See again that He has not said, I know not when the time will be, but, "Ye know not." For the reason why He concealed it was that it was better for us; for if, now that we know not the end, we are careless, what should we do if we knew it? We should keep on our wickedness even unto the end. Let us therefore attend to His words; for the end comes at even, when a man dies in old age; a midnight, when he dies in the midst of his youth; and at cockcrow, when our reason is perfect within us; for when a child begins to live according to his reason, then the cock cries loud within him, rousing him from the sleep of sense; but the age of childhood is the morning. Now all these ages must look out for the end; for even a child must be watched, lest he die unbaptized.
Pseudo-Jerome - He thus concludes His discourse, that the last should hear from those who come first this precept which is common to all; wherefore He adds, "But what I say unto you I say unto all, Watch."
Augustine, Epist., 199, 3 - 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.
- text taken from Catena Aurea - Gospel of Mark by Saint Thomas Aquinas, translated by William Whiston, 1842