“Watch ye therefore: for ye know not when the master of the house cometh, at even, or at midnight, or at the cockcrowing, or in the morning:”
Therefore keep watch, because you do not know when the owner of the house will come back — whether in the evening, or at midnight, or when the rooster crows, or at dawn — the four watches of the night (evening, midnight, rooster-crow, dawn) are the four-part Roman division of the night watch. Each watch is named to communicate that the return could come at any time within the period of waiting. The four watches of the night correspond exactly to the four scenes of Jesus' passion night (evening — Last Supper, midnight — Gethsemane, rooster-crow — Peter's denial, dawn — the morning trial).
Church Fathers on Mark 13:35
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.'
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…
For we must needs watch with our souls before the death of the body.