Gregory the Great
Catena Aurea · Markusevangelium 13
But of that day and that hour knoweth no man, no, not the angels which are in heaven, neither the Son, but the Father. Take ye heed, watch and pray: for ye know not when the time is. For the Son of man is as a man taking a far journey, who left his house, and gave authority to his servants, and to every man his work, and commanded the porter to watch. 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: Lest coming suddenly he find you sleeping. And what I say unto you I say unto all, Watch.
(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.